"'Conjoined twins" are identical twins joined in utero. An extremely rare phenomenon, the occurrence is estimated to range from 1 in 49,000 births to 1 in 189,000 births, with a somewhat higher incidence in Southeast Asia and Africa. Approximately half are stillborn, and an additional one-third die within 24 hours. Most live births are female, with a ratio of 3:1.

Two contradicting theories exist to explain the origins of conjoined twins. The more generally accepted theory is "fission", in which the fertilized egg splits partially. The other theory, no longer believed to be the basis of conjoined twinning, is fusion, in which a fertilized egg completely separates, but stem cells (which search for similar cells) find like-stem cells on the other twin and fuse the twins together. Conjoined twins share a single common chorion, placenta, and amniotic sac, although these characteristics are not exclusive to conjoined twins as there are some monozygotic but non-conjoined twins who also share these structures in utero.

The most famous pair of conjoined twins was Chang and Eng Bunker (Thai: อิน-จัน, In-Chan) (1811–1874), Thai brothers born in Siam, now Thailand. They traveled with P.T. Barnum's circus for many years and were labeled as the Siamese twins. Chang and Eng were joined at the torso by a band of flesh, cartilage, and their fused livers. In modern times, they could have been easily separated. Due to the brothers' fame and the rarity of the condition, the term "Siamese twins" came to be used as a synonym for conjoined twins.

Republican marriage () was a method of execution that allegedly occurred in Nantes during the Reign of Terror in Revolutionary France and "involved tying a naked man and woman together and drowning them". This was reported to have been practised during the drownings at Nantes ("noyades") that were ordered by local Jacobin representative-on-mission Jean-Baptiste Carrier between November 1793 and January 1794 in the city of Nantes. Most accounts indicate that the victims were drowned in the Loire River, although a few sources describe an alternative means of execution in which the bound couple is run through with a sword, either before, or instead of drowning.

The earliest reports of such "marriages" date from 1794, when Carrier was tried for his crimes, and they were soon cited by contemporary counter-revolutionary authors such as Louis-Marie Prudhomme and Louis Gabriel Ambroise de Bonald.

Ilona and Judit Gófitz (Hungarian: "Gófitz Ilona" és "Judit"; in contemporary publications: "Helen" and "Judith of Szőny"), also known as the Hungarian Sisters, were conjoined twins from Szőny, Hungary who lived from October 19, 1701 to February 8, 1723. In the image they appear to be pygopagus.

The phenomenon known as Beatlemania originated in the United Kingdom, birthplace of the Beatles, when the band first realised enormous popularity there in 1963. Returning in 1962 from a highly formative two-year residency in Germany, the Beatles achieved a commercial breakthrough with their second UK single release, "Please Please Me" early in 1963, but gained "Superstar" status with the release of "She Loves You" later that year. There followed an almost non-stop series of concerts and tours, attended with feverish enthusiasm across the UK, for the whole of the following year. The Beatles' popularity in the UK came to exceed even that of the notable American artists Tommy Roe, Chris Montez and Roy Orbison, whose UK chart success at the time did not keep them from being overshadowed by the Beatles during their 1963 nationwide tours with the lower-billed band — an achievement previously unknown for a UK act.

With intense media interest in the Beatles during 1963, the year was also taken up with TV shows, press interviews and a weekly radio show. Despite these demands the band found time for many sessions in the recording studio, releasing two albums and four singles during the year. 1963 was also the year when Lennon's son Julian was born.

By the end of 1963, Beatlemania would begin to spread internationally. The single "I Want to Hold Your Hand" entered the US charts on 18 January 1964, selling one-and-a-half million copies in under three weeks, and the following month the Beatles made their first visit to America. The great interest in the Beatles brought about a major change in US attitudes to popular music and marked the start of the phenomenon known as the British Invasion.

Embryo splitting in which zygote divide asexually,

to produce identical children, is blocked by mitosis inhibitor.

During the year prior to the 2015 U.S. survey, 59 percent of respondents reported avoiding using a public restroom out of fear of violence or harassment. 32 percent limited the amount they ate or drink in order to avoid using a public restroom. Eight percent reported suffering a urinary tract infection, kidney infection, or other kidney problem as a result of avoiding public restrooms.

Thirty-three percent reported having negative experiences with a healthcare professional related to being transgender, such as verbal harassment or denial of treatment. 23 percent reported that they did not seek treatment for a condition out of fear of being mistreated, while 33 percent did not seek treatment because they were unable to afford it.

During the month prior to the survey, 39 percent of American transgender people experienced major psychological distress, compared to 5 percent of the general population of the United States. 40 percent had attempted suicide at some point in their life, compared to 4.6 percent of the American population. Family and community support were correlated with far lower rates of suicide attempts and of major psychological distress.

A study conducted on transgender women of color in San Francisco has shown a higher correlation between transphobia and risk of transgender women engaging in HIV risk behavior. The study shows that the transgender youth face social discrimination, and they may not have a social role model. The young adults in this group have shown a higher risk of engaging in unprotected receptive anal intercourse when the exposure to transphobia is high. Therefore, as per the study shows a correlation between transphobia and high risk of HIV.

Cryptomnesia occurs when a forgotten memory returns without it being recognized as such by the subject, who believes it is something new and original. It is a memory bias whereby a person may falsely recall generating a thought, an idea, a tune, or a joke, not deliberately engaging in plagiarism but rather experiencing a memory as if it were a new inspiration.

Islamophobia is an intense fear or hatred of, or prejudice against, the Islamic religion or Muslims, especially when seen as a geopolitical force or the source of terrorism.

The term was first used in the early 20th century and it emerged as a neologism in the 1970s, then it became increasingly salient during the 1980s and 1990s, and it reached public policy prominence with the report by the Runnymede Trust's Commission on British Muslims and Islamophobia (CBMI) entitled "Islamophobia: A Challenge for Us All" (1997). The introduction of the term was justified by the report's assessment that "anti-Muslim prejudice has grown so considerably and so rapidly in recent years that a new item in the vocabulary is needed".

The causes and characteristics of Islamophobia are still debated. Some commentators have posited an increase in Islamophobia resulting from the September 11 attacks, some from multiple terror attacks in Europe and the United States, while others have associated it with the increased presence of Muslims in the United States and in the European Union. Some people also question the validity of the term. The academics S. Sayyid and Abdoolkarim Vakil maintain that Islamophobia is a response to the emergence of a distinct Muslim public identity globally, the presence of Muslims is in itself not an indicator of the degree of Islamophobia in a society. Sayyid and Vakil maintain that there are societies where virtually no Muslims live but many institutionalized forms of Islamophobia still exist in them.

Radiation, most commonly in the form of X-rays, is used frequently in society in order to produce positive outcomes. The primary use of radiation in healthcare is in the use of radiography for radiographic examination or procedure, and in the use of radiotherapy in the treatment of cancerous conditions. Radiophobia can be a fear which patients experience before and after either of these procedures, it is therefore the responsibility of the healthcare professional at the time, often a Radiographer or Radiation Therapist, to reassure the patients about the stochastic and deterministic effects of radiation on human physiology. Advising patients and other irradiated persons of the various radiation protection measures that are enforced, including the use of lead-rubber aprons, dosimetry and Automatic Exposure Control (AEC) is a common method of informing and reassuring radiophobia sufferers.

Similarly, in industrial radiography there is the possibility of persons to experience radiophobia when radiophobia sufferers are near industrial radiographic equipment.

Transphobia is a range of negative attitudes, feelings or actions toward transgender or transsexual people, or toward transsexuality. Transphobia can be emotional disgust, fear, violence, anger or discomfort felt or expressed towards people who do not conform to society's gender expectations. It is often expressed alongside homophobic views and hence is often considered an aspect of homophobia. Transphobia is a type of prejudice and discrimination similar to racism and sexism, and transgender people of color are often subjected to all three forms of discrimination at once.

Child victims of transphobia experience harassment, school bullying, and violence in school, foster care, and social programs. Adult victims experience public ridicule, harassment including misgendering, taunts, threats of violence, robbery, and false arrest; many feel unsafe in public. A high percentage report being victims of sexual violence. Some are refused healthcare or suffer workplace discrimination, including being fired for being transgender, or feel under siege by conservative political or religious groups who oppose laws to protect them. There is even discrimination from some people within the movement for the rights of gender and sexual minorities.

Besides the increased risk of violence and other threats, the stress created by transphobia can cause negative emotional consequences which may lead to substance abuse, running away from home (in minors), and a higher rate of suicide.

In the Western world, there have been gradual changes towards the establishment of policies of non-discrimination and equal opportunity. The trend is also taking shape in developing nations. In addition, campaigns regarding the LGBT community are being spread around the world to improve acceptance; the "Stop the Stigma" campaign by the UN is one such development.

Like astraphobia, lilapsophobia is a common fear for children, although less common. Because children are just learning to distinguish between fantasy and reality, major storm broadcasts on television or discussion by parents can cause fear that the storm is coming with a tornadic potential or a hurricane.

Because fear is a part of normal child development, this phobia is not diagnosed unless if persisted for more than six months. Parents should conquer the child's fear by telling them how rare the major storms that hit hometown area are.

Transmisogyny (sometimes trans-misogyny) is the intersection of transphobia and misogyny. Transphobia is defined as "the irrational fear of, aversion to, or discrimination against transgender or transsexual people". Misogyny is defined as "a hatred of women". Therefore, transmisogyny includes negative attitudes, hate, and discrimination of transgender or transsexual individuals who fall on the feminine side of the gender spectrum, particularly transgender women. The term was coined by Julia Serano in her 2007 book "Whipping Girl" and used to describe the unique discrimination faced by trans women because of "the assumption that femaleness and femininity are inferior to, and exist primarily for the benefit of, maleness and masculinity", and the way that transphobia intensifies the misogyny faced by trans women (and vice versa). It is said many trans women experience an additional layer of misogyny in the form of fetishization; Serano talks about how society views trans women in certain ways that sexualize them, such as them transitioning for sexual reasons, or ways where they’re seen as sexually promiscuous.Transmisogyny is a central concept in transfeminism and is commonly referenced in intersectional feminist theory. That trans women's femaleness (rather than only their femininity) is a source of transmisogyny is denied by certain radical feminists, who claim that trans women are not female.

Lilapsophobes spend a lot of time watching the weather or checking weather online to keep an eye out for oncoming storms. When a storm hits, sufferers either watch for severe weather alerts constantly or take cover, like under the bed or in the windowless room. In the extreme cases, sufferers take tornado shelter as soon as rain starts falling, usually in the basement or storm shelter. Sufferers who have weather radio or mobile phones can watch the radar and alerts using it while hiding.

Radiophobia is an obsessive fear of ionizing radiation, in particular, fear of X-rays. While in some cases radiation may be harmful (i.e. radiation-induced cancer, and acute radiation syndrome), the effects of poor information, understanding, or a traumatic experience may cause unnecessary or even irrational fear. The term is also used in a non-medical sense to describe the opposition to the use of nuclear technology (i.e. nuclear power) arising from concerns disproportionately greater than actual risks would merit.

Transmisogyny is generally understood to be caused by the social belief that men are superior to women. In "Whipping Girl", Julia Serano writes that the existence of trans women is seen as a threat to a "male-centered gender hierarchy, where it is assumed that men are better than women and that masculinity is superior to femininity". Gender theorist Judith Butler echoes this assumption, stating that the murder of transgender women is "an act of power, a way of re-asserting domination... killing establishes the killer as sovereign in the moment that he kills".

Trans women are also viewed as threatening the heterosexuality of cisgender men. In media, "deceivers" such as Dil, a transgender woman from the 1992 film "The Crying Game", have been observed to invoke outrage and male homophobia in an audience when their "true" maleness is unveiled.

The fear of crime refers to the fear of being a victim of crime as opposed to the actual probability of being a victim of crime.

The fear of crime, along with fear of the streets and the fear of youth, is said to have been in Western culture for "time immemorial". While fear of crime can be differentiated into public feelings, thoughts and behaviors about the personal risk of criminal victimization, distinctions can also be made between the tendency to see situations as fearful, the actual experience while in those situations, and broader expressions about the cultural and social significance of crime and symbols of crime in people's neighborhoods and in their daily, symbolic lives.

Importantly, feelings, thoughts and behaviors can have a number of functional and dysfunctional effects on individual and group life, depending on actual risk and people's subjective approaches to danger. On a negative side, they can erode public health and psychological well-being; they can alter routine activities and habits; they can contribute to some places turning into 'no-go' areas via a withdrawal from community; and they can drain community cohesion, trust and neighborhood stability. Some degree of emotional response can be healthy: psychologists have long highlighted the fact that some degree of worry can be a problem-solving activity, motivating care and precaution, underlining the distinction between low-level anxieties that motivate caution and counter-productive worries that damage well-being.

Factors influencing the fear of crime include the psychology of risk perception, circulating representations of the risk of victimization (chiefly via interpersonal communication and the mass media), public perceptions of neighborhood stability and breakdown, the influence of neighbourhood context, and broader factors where anxieties about crime express anxieties about the pace and direction of social change. There are also some wider cultural influences. For example, some have argued that modern times have left people especially sensitive to issues of safety and insecurity.

Transsexual people experience a gender identity that is inconsistent with, or not culturally associated with, their assigned sex, and desire to permanently transition to the gender with which they identify, usually seeking medical assistance (including hormone replacement therapy and other sex reassignment therapies) to help them align their body with their identified sex or gender.

"Transsexual" is generally considered a subset of "transgender", but some transsexual people reject the label of "transgender". A medical diagnosis of gender dysphoria can be made if a person expresses a desire to live and be accepted as a member of their identified sex, and if a person experiences impaired functioning or distress as a result of their gender identity.

Estimates of the prevalence of transgender people are highly dependent on the specific case definitions used in the studies, with prevalence rates varying by orders of magnitude. The most frequently quoted estimate of prevalence is from the Amsterdam Gender Dysphoria Clinic; over four decades the clinic has treated roughly 95% of Dutch transsexual clients, and it suggests a prevalence of 1:10,000 among assigned males and 1:30,000 among assigned females. In the US, the DSM-IV (1994) says that roughly 1 in 30,000 assigned males and 1 in 100,000 assigned females seek sex reassignment surgery. Though no direct studies on the prevalence of GID have been done, a variety of clinical papers published in the past 20 years provide estimates ranging from 1:7,400 to 1:42,000 in assigned males and 1:30,040 to 1:104,000 in assigned females. A 2008 study of the number of New Zealand passport holders who changed the sex on their passport estimated that 1:3,639 birth-assigned males and 1:22,714 birth-assigned females were transsexual.

The most recent (2016) systematic review of prevalence, leading to a meta-analysis of 27 studies, found estimates per 100,000 population of 9.2 (95% CI = 4.9–13.6) for surgical or hormonal gender affirmation therapy and 6.8 (95% CI = 4.6–9.1) for transgender-related diagnoses. Of studies assessing self-reported transgender identity, prevalence was 871 (95% CI = 519–1,224); however, this result was influenced by a single outlier study. After removal of that study, the figure dropped to 355 (95% CI = 144–566). Significant heterogeneity was observed in most analyses.

Olyslager and Conway presented a paper at the WPATH 20th International Symposium (2007) arguing that the data from their own and other studies actually imply much higher prevalence, with minimum lower bounds of 1:4,500 male-to-female transsexual people and 1:8,000 female-to-male transsexual people for a number of countries worldwide. They estimate the number of post-op women in the US to be 32,000 and obtain a figure of 1:2500 male-to-female transsexual people. They further compare the annual incidences of SRS and male birth in the U.S. to obtain a figure of 1:1000 MTF transsexual people and suggest a prevalence of 1:500 extrapolated from the rising rates of SRS in the US and a "common sense" estimate of the number of undiagnosed transsexual people. Olyslager and Conway also argue that the US population of assigned males having already undergone reassignment surgery by the top three US SRS surgeons alone is enough to account for the entire transsexual population implied by the 1:10,000 prevalence number, yet this excludes all other US SRS surgeons, surgeons in countries such as Thailand, Canada, and others, and the high proportion of transsexual people who have not yet sought treatment, suggesting that a prevalence of 1:10,000 is too low.

A study of Swedes estimated a ratio of 1.4:1 trans women to trans men for those requesting sex reassignment surgery and a ratio of 1:1 for those who proceeded.

A presentation at the LGBT Health Summit in Bristol, UK, based upon figures from a number of reputable European and UK sources, shows that this population is increasing rapidly (14% per year) and that the mean age of transition is actually rising.

In 2015, the National Center for Transgender Equality conducted a National Transgender Discrimination Survey. Of the 27,715 transgender and non-binary people who took the survey, 35% identified as non-binary, 33% identified as transgender women, 29% identified as transgender men, and 3% said that "crossdresser" best described their gender identity.

The College of Optometrists (UK) has specified guidelines for optometrists who use the colorimeter system. A society for coloured lens prescribers has been established to provide a list of eye-care practitioners with expertise in the provision of coloured lenses for the treatment of visual stress.

Irlen syndrome, occasionally referred to as scotopic sensitivity syndrome (SSS) or Meares-Irlen syndrome, very rarely as asfedia, and recently also as visual stress, is a proposed disorder of vision.

Homophobia encompasses a range of negative attitudes and feelings toward homosexuality or people who are identified or perceived as being lesbian, gay, bisexual or transgender (LGBT). It has been defined as contempt, prejudice, aversion, hatred or antipathy, may be based on irrational fear, and is often related to religious beliefs.

Homophobia is observable in critical and hostile behavior such as discrimination and violence on the basis of sexual orientations that are non-heterosexual. Recognized types of homophobia include "institutionalized" homophobia, e.g. religious homophobia and state-sponsored homophobia, and "internalized" homophobia, experienced by people who have same-sex attractions, regardless of how they identify.

Negative attitudes toward identifiable LGBT groups have similar yet specific names: lesbophobia is the intersection of homophobia and sexism directed against lesbians, biphobia targets bisexuality and bisexual people, and transphobia targets transgender and transsexual people and gender variance or gender role nonconformity. According to 2010 Hate Crimes Statistics released by the FBI National Press Office, 19.3 percent of hate crimes across the United States "were motivated by a sexual orientation bias." Moreover, in a Southern Poverty Law Center 2010 "Intelligence Report" extrapolating data from fourteen years (1995–2008), which had complete data available at the time, of the FBI's national hate crime statistics found that LGBT people were "far more likely than any other minority group in the United States to be victimized by violent hate crime."

The term "homophobia" and its usage have been criticized by several sources as unwarrantedly pejorative

Deafblindness is the condition of little or no useful sight and little or no useful hearing. Educationally, individuals are considered to be deaf-blind when the combination of their hearing and sight loss causes such severe communication and other developmental and educational needs that they require significant and unique adaptations in their educational programs. Helen Keller was one such individual.

Macrophilia is a fascination with or a sexual fantasy involving giants, more commonly expressed as giantesses (female giants). It is typically a male fantasy, with the male playing the "smaller" part—entering, being dominated, or being eaten by the larger woman. Others involve partners who naturally have a significant difference in size.

Blindness can occur in combination with such conditions as intellectual disability, autism spectrum disorders, cerebral palsy, hearing impairments, and epilepsy. Blindness in combination with hearing loss is known as deafblindness.

It has been estimated that over half of completely blind people have non-24-hour sleep–wake disorder, a condition in which a person's circadian rhythm, normally slightly longer than 24 hours, is not entrained (synchronized) to the light/dark cycle.

Although macrophilia literally translates to simply a "lover of large," in the context of a sexual fantasy, it is used to mean someone who is attracted to beings larger than themselves. Generally, the interest differs between people, and depends on gender and sexual orientation. They often enjoy feeling small and being abused, degraded, dominated, or eaten, and they may also view female giants as being powerful and dominating.

Commenting on why there are not as many female macrophiles, psychologist Helen Friedman theorized that because women in most societies already view men as dominant and powerful, there is no need for them to fantasize about it. Women that take on the roles of the giantess within this fetish often find the practice to be empowering and enjoy being worshipped.

The roots of macrophilia may lie in sexual arousal in childhood and early adolescence which is accidentally associated with giants, according to Dr. Mark Griffiths's speculation.