Etymology and Definitions

The word comes from the Greek: παῖς (paîs), meaning "child," and φιλία (philía), "friendly love" or "friendship". This literal meaning has been altered toward sexual attraction in modern times, under the titles "child love" or "child lover," by pedophiles who use symbols and codes to identify their preferences.

Nepiophilia is used to refer to a sexual preference for infants and toddlers (usually ages 0–3), pedophilia is used for individuals with a primary sexual interest in prepubescent children aged 13 or younger, and hebephilia is defined as individuals with a primary sexual interest in 11-14 year old pubescents. The DSM IV does not list hebephilia among the diagnoses, while the ICD-10 includes hebephilia in its pedophilia definition, covering the physical development overlap between the two philias.

Some clinicians have proposed further cateogories, somewhat or completely distinguished from pedophilia, including "pedohebephilia," "hebephilia," and "ephebophilia" (though ephebophilia is not considered pathological).

Disease models
The term paedophilia erotica was coined in 1886 by the Viennese psychiatrist Richard von Krafft-Ebing in his writing Psychopathia Sexualis. The term appears in a section titled "Violation of Individuals Under the Age of Fourteen," which focuses on the forensic psychiatry aspect of child sexual offenders in general. Krafft-Ebing describes several typologies of offender, dividing them into psychopathological and non-psychopathological origins, and hypothesizes several apparent causal factors that may lead to the sexual abuse of children.

Krafft-Ebing mentioned paedophilia erotica in a typology of "psycho-sexual perversion." He wrote that he had only encountered it four times in his career and gave brief descriptions of each case, listing three common traits:

    The individual is tainted (hereditär belastate)
    The subject's primary attraction is to children, rather than adults.
    The acts committed by the subject are typically not intercourse, but rather involve inappropriate touching or manipulating the child into performing an act on the subject.

He mentions several cases of pedophilia among adult women (provided by another physician), and also considered the abuse of boys by homosexual men to be extremely rare. Further clarifying this point, he indicated that cases of adult men who have some medical or neurological disorder and abuse a male child are not true pedophilia, and that in his observation victims of such men tended to be older and pubescent. He also lists "Pseudopaedophilia" as a related condition wherein "individuals who have lost libido for the adult through masturbation and subsequently turn to children for the gratification of their sexual appetite" and claimed this is much more common.

In 1908, Swiss neuroanatomist and psychiatrist Auguste Forel wrote of the phenomenon, proposing that it be referred to it as "Pederosis," the "Sexual Appetite for Children." Similar to Krafft-Ebing's work, Forel made the distinction between incidental sexual abuse by persons with dementia and other organic brain conditions, and the truly preferential and sometimes exclusive sexual desire for children. However, he disagreed with Krafft-Ebing in that he felt the condition of the latter was largely ingrained and unchangeable.

The term "pedophilia" became the generally accepted term for the condition and saw widespread adoption in the early 20th century, appearing in many popular medical dictionaries such as the 5th Edition of Stedman's in 1918. In 1952, it was included in the first edition of the Diagnostic and Statistical Manual of Mental Disorders. This edition and the subsequent DSM-II listed the disorder as one subtype of the classification "Sexual Deviation," but no diagnostic criteria were provided. The DSM-III, published in 1980, contained a full description of the disorder and provided a set of guidelines for diagnosis. The revision in 1987, the DSM-III-R, kept the description largely the same, but updated and expanded the diagnostic criteria.

Diagnostic criteria
ICD-10 and DSM
The ICD-10 defines pedophilia as "a sexual preference for children, boys or girls or both, usually of prepubertal or early pubertal age." Under this system's criteria, a person 16 years of age or older meets the definition if they have a persistent or predominant sexual preference for prepubescent children at least five years younger than them.

The Diagnostic and Statistical Manual of Mental Disorders 4th edition Text Revision (DSM-IV-TR) outlines specific criteria for use in the diagnosis of this disorder. These include the presence of sexually arousing fantasies, behaviors or urges that involve some kind of sexual activity with a prepubescent child (age 13 or younger, though onset of puberty may vary) for six months or more, and that the subject has acted on these urges or suffers from distress as a result of having these feelings. The criteria also indicate that the subject should be 16 or older and that the child or children they fantasize about are at least five years younger than them, though ongoing sexual relationships between a 12-13 year old and a late adolescent are advised to be excluded. A diagnosis is further specified by the sex of the children the person is attracted to, if the impulses or acts are limited to incest, and if the attraction is "exclusive" or "nonexclusive."

Many terms have been used to distinguish "true pedophiles" from non-pedophilic and non-exclusive offenders, or to distinguish among types of offenders on a continuum according to strength and exclusivity of pedophilic interest, and motivation for the offense (see child sexual offender types). Exclusive pedophiles are sometimes referred to as "true pedophiles." They are attracted to prepubescent children, and prepubescent children only. They show no erotic interest in adults their own age and can only become aroused while fantasizing about or being in the presence of prepubescent children, or both. Non-exclusive offenders — or "non-exclusive pedophiles" — may at times be referred to as non-pedophilic offenders, but the two terms are not always synonymous. Non-exclusive offenders are attracted to both children and adults, and can be sexually aroused by both, though a sexual preference for one over the other in this case may also exist. If a preference for prepubescent children, such offenders are considered pedophiles in the same vein as exclusive offenders.

Neither the ICD nor the DSM diagnostic criteria require actual sexual activity with a prepubescent youth. The diagnosis can therefore be made based on the presence of fantasies or sexual urges even if they have never been acted upon. On the other hand, a person who acts upon these urges yet experiences no distress about their fantasies or urges can also qualify for the diagnosis. Acting on sexual urges is not limited to overt sex acts for purposes of this diagnosis, and can sometimes include indecent exposure, voyeuristic or frotteuristic behaviors, or masturbating to child pornography. Often, these behaviors need to be considered in-context with an element of clinical judgment before a diagnosis is made. Likewise, when the patient is in late adolescence, the age difference is not specified in hard numbers and instead requires careful consideration of the situation.

Ego-dystonic sexual orientation (F66.1) includes people who acknowledge that they have a sexual preference for prepubertal children, but wish to change it due to the associated psychological or behavioral problems (or both).
Debate regarding the DSM criteria

The DSM IV criteria have been criticized simultaneously for being over-inclusive, as well as under-inclusive. Though most researchers distinguish between child molesters and pedophiles, Studer and Aylwin argue that the DSM criteria are over-inclusive because all acts of child molestation warrant the diagnosis. A child molester satisfies criteria A because of the behavior involving sexual activity with prepubescent children and criteria B because the individual has acted on those urges. Furthermore, they argue that it also is under-inclusive in the case of individuals who do not act upon it and are not distressed by it. The latter point has also been made by several other researchers who have remarked that a so-called "contented pedophile"—an individual who fantasizes about having sex with a child and masturbates to these fantasies, but does not commit child sexual abuse, and who does not feel subjectively distressed afterward—does not meet the DSM-IV-TR criteria for pedophilia, because this person does not meet Criterion B. A large-scale survey about usage of different classification systems showed that the DSM classification is only rarely used. As an explanation, it was suggested that the under-inclusiveness, as well as a lack of validity, reliability and clarity might have led to the rejection of the DSM classification.

Ray Blanchard, in his literature review for the DSM-5, noted the objections and proposed a general solution applicable to all paraphilias, namely a distinction between paraphilia and paraphilic disorder. The latter term is proposed to identify the diagnosable condition, which meets both Criterion A and B, whereas an individual who does not meet Criterion B, can be ascertained, but not diagnosed, as having a paraphilia. The current proposals for the DSM V will also resolve the current physical development overlap between pedophilia and hebephilia by combining them under Pedophilic Disorder, but with specifiers on which age range (or both) is the primary interest. This new diagnosis would be equivalent to the ICD-10 definition of pedophilia that already includes early pubescents.

O'Donohue, however, took the issue in a different direction, suggesting instead that the diagnostic criteria be simplified to the attraction to children alone if ascertained by self-report, laboratory findings, or past behavior. He states that any sexual attraction to children is pathological and that distress is irrelevant, noting "this sexual attraction has the potential to cause significant harm to others and is also not in the best interests of the individual." Also arguing for behavioral criteria in defining pedophilia, Howard E. Barbaree and Michael C. Seto disagreed with the American Psychiatric Association's approach in 1997 and instead recommended the use of actions as the sole criterion for the diagnosis of pedophilia, as a means of taxonomic simplification.

Other uses
In a 1993 review of research on child sexual abuse, Sharon Araji and David Finkelhor stated that because this field of research was underdeveloped at that time, there are "definitional problems" resulting from lack of standardization among researchers in their use of the term "pedophilia." They described two definitions, a "restrictive" form referring to individuals with strong and exclusive sexual interest in children, and an "inclusive" definition, expanding the term to include offenders who engaged in sexual contact with a child, including incest. They stated that they used the wider definition in their review paper because behavioral criteria are easier to identify and do not require complex analysis of an individual's motivations.