A boy is a young male (usually child or adolescent), as contrasted to its female counterpart, girl; thus in the wide sense of both terms all mankind, and in the strictest sense youth, consists of 'boys and girls'.
The term "boy" is primarily used to indicate biological sex distinctions, cultural gender role distinctions or both. The latter most commonly applies to adult men, either considered in some way immature or inferior, in a position associated with aspects of boyhood, or even without such boyish connotation as age-indiscriminate synonym. The term can be joined with a variety of other words to form these gender-related labels as compound words.
Ongoing debates about the influences of nature versus nurture in shaping the behavior of girls and boys raises questions about whether the roles played by boys are mainly the result of inborn differences or of socialization. Images of boys in art, literature and popular culture often demonstrate assumptions about gender roles.
The age boundary is not clear cut, rather dependent on the context or even on individual circumstances. A young man who has not assumed (or has been denied) the traditional roles of a man might also be called a boy. It may feel uncomfortable to a young male upon being referred to as a "man" before he believes he has assumed these roles, such as having a career, a partner, a household of his own, fatherhood. Conversely, it may feel uncomfortable to a male to be called a "boy" if he believes he has assumed the traditional roles of a "man". In mother's/mama's boy, the word emphatically implies a male (minor or adult in years) who is too immature to be independent.
In some traditions boyhood is held to be exchanged for adult manhood, or at least approach it significantly, by certain -in se independent- acts assuming a role deemed to be typical for a "normal" man (though there are limits) as marriage, fathering offspring or military service. Various cultural and/or religious rites of passage serve, partially or specifically, to mark the transition to manhood. There is often a number of traditional differences in attire between boys and adult men, which may even give rise to a metaphoric term such as broekvent in Dutch (i.e., a boy who has not yet "graduated" from shorts to trousers) and in what is socially accepted as appropriate behaviour, e.g., boys may be publicly seen naked in cultures where men are not.
In English, the words youth, teenager and adolescent may refer to either male or female. No gender-specific term exists for an intermediate stage between a boy and a man, except "young man", although the term puberty, for one who reached sexual reproductivity (or the legally assumed age, e.g. 14 for boys, often set lower for girls) without being a legal adult yet, stems from a Latin word for boys only, itself named after the accompanying male body hair, pubes, on face and genital region.
Many occasions occur when an adult male is commonly referred to as a boy. A person's boyfriend or loverboy may be of any age; this even applies to a 'working' call-boy, toyboy (though usually younger than the client as youth is generally considered attractive). Reflecting the general aesthetic preference for youth, one says pretty boy (e.g. in the nickname of Charles Arthur "Pretty Boy" Floyd, who committed his first bank robbery at age 30) or Adonis (name of a mythological youth) even when a male beauty is clearly of riper age. In terms (used pejoratively or neutrally) for homosexuals such as batty boy (alongside "batty man"; from "bottom") or "bum boy", age is not essential, but the connotation of immaturity can strengthen insulting use.
A man's group of male friends etc. engaged in Male bonding are often called "the boys". It is most common to refer to men, irrespective of age or even in an adult age group, as boys in the context of a team (especially all-male), such as old boys for networking of adult men who attended the same school(s) as boys, or as professional colleagues, e.g. "the boys at the office, - police station etc." (often all adults). The members of a student fraternity can be called frat(ernity) boys, technically preferable to the pleonasm frat-bro(ther), and remain so for life as adults, after graduation.
In sports 'the boys' commonly refers to the teammates; e.g., UK football managers quite often refer to their players as "The boy so-and-so" and this usage is by no means restricted to the youngest players, though it is rarely applied to the most senior.
In US urban, particularly African American and Latino slang the term boy is used with a possessive as meaning friend (my boy, his boys), presumably as a reduction of homeboy, originally a male from the same area.
In some cases, a word using boy is used merely to designate the age of the (male) person, irrespective of the function, as in altar boy, a minor acting as liturgical acolyte, or in Boy Scouts, an organisation specifically for boys. Thus the compound -man can then be replaced by -boy, as in footboy; or boy is simply added, either as a prefix (e.g., in boy-racer) or as a suffix (e.g., in Teddy Boy).
An adult equivalent (with or without -man) is not to be expected when -boy designates an apprentice (for which some languages use a compound with the equivalent of boy, e.g. leerjongen 'learning boy' in Dutch) or lowest rank implying specific on the job training if promotion is to be obtained, as in kitchen-boy. Similarly schoolboy only applies to minors; the modern near-synonym pupil originally designated a minor in Roman law as being under a specific adult's authority, as in loco parentis.
Expressions such as "boys will be boys" (i.e., a male always retains a tendency for boyish games or mischief) allude to stereotypically ascribed characteristics of boys and men; in the term tomboy, a woman's (according to the counterpart-gender stereotype) uncharacteristically bold nature is even described solely by comparing her to a boy.
The use of boy (like kid) in (fantasy or descriptive) nick-names, also for adult men (e.g. Shark Boy for a wrestler with matching costume), may also connote to the informal or naughty image of boyhood.
In such terms as 'city boy' or 'home boy', the age notion is at most anachronistic, as they indicate any male who grew up (or by extension lived a long time) in a certain environment.
They also show that similar semantic broadness applies to many languages, notably Indo-European; to avoid lengthy duplication, cases may simply be linked here.
A case where the term is formally used for (adult) men is sideboy, a member of an even-numbered group of seaman posted in two rows at the Quarterdeck when a visiting dignitary boards or leaves a ship.
In the Ottoman empire, the young, mainly Christian military recruits for life (often forcibly enlisted by 'devshirme') were officially called acemi oglanlar ("novice boys").
Thus "-boy" can enter the nickname for a particular nation's soldiers, e.g. the US (infantry) doughboy, or a specific force, e.g. Fly-boy is slang for an airman. Furthermore, specific terms refer to minors used in the armed forces:
However, when a minor in military employ is considered (historically often far less restrictive then nowadays) too young to be a 'normal' warrior (illegal under present UN rules, but without precise enforceable age limits), he's called boy soldier, regardless whether he's used as an armed fighter or only in logistic or similar functions such as bearer.
Certain jobs need so little training or formal qualifications that they can easily be performed as student job, and thus tend to be filled mostly or exclusively by minors, as it would not pay to employ an adult at or above minimum wage. Thus an equivalent word with the compound man (or similar) may be the rarer one, or even inexistent. Examples include delivery boy, errand boy, messenger boy and various specific terms naming the product to deliver, such as paperboy (closest adult counterpart postman), pizza boy (alongside pizzaman), or to serve, such as a potboy (drinks waiter). In other cases the compound mentions a crucial attribute of his task, e.g. ballboy (more recently also girls) in tennis. In some cases his small, light body makes a boy a better choice, e.g. as jockey where no weight handicap is in force.
Again by analogy "boy" can occasionally even refer to a 'male' object.
Some words contain 'boy' in English by mistake (folk etymology), actually referring to a (near) homophone such as French bois = "wood" (e.g. in "low boy", a type of furniture, and in "tallboy", both furniture and a high glass or goblet).
Many mythological boys have frequently been represented in various arts, e.g. Venus' often mischievous son Cupid, himself a young god of love which he 'inflicts' on humans by shooting his arrows; in some style periods even multiplied as naked little boys called putti.
In portrait art, and generally in commissioned work (including funeral art), the subjects are usually determined by the wishes of the (adult) client, so minors are often in the minority, yet in wealthy families especially heirs are (re)presented as part of their social positioning in view of future marriage and succession, generally either as mini-adults or stereotypical youth, e.g. at play or in cozy home scenes.
Some artists displayed a clear predeliction for scenes with boys, in certain cases (especially if frequently depicting revealing poses) believed to have to do with a homo-erotic taste, as is believed of the highly respected Old Master Caravaggio, or Henry Scott Tuke who kept producing such works even though the market circa 1900 was rather unappreciative.
In music, boys' voices, before they 'break' being of a soprano register (specifically known as treble) unlike adult men (in a choir usually tenor and bass), have been most sought-after, especially where female voices were considered inappropriate as often in church and certain theatrical music - this even lead to the practice of physically trying to prevent their 'angelical' voices ever to break by surgically cutting short the hormonal drive to manhood: for centuries, castrato singers, who coupled adult strength and experience with a treble register, starred in contratenor parts, mainly in operatic styles.