Boy

Historically, in the United States and South Africa, "boy" was not only a "neutral" term for domestics but also a disparaging term towards men of color; the term implied a subservient status.[3][4][5][6] The use of the term "boy" to describe men of color has not always been used as an insult, however; for example, Thomas Branch, an early African-American Seventh-day Adventist missionary to Nyassaland (Malawi) referred to the native students as boys:

There is one way by which we judge many of our present boys to be quite different from some of those who were here long ago: those that are married have their wives here with them, and build their own houses, and all are busy making their gardens. I have told all the boys that if they wished to stay here and learn, those that had wives must bring them. This is having a good effect on them. They stay longer, and are more attentive to their work and their studies.[7]

Multiple politicians – including New Jersey Governor Chris Christie and former Kentucky Congressman Geoff Davis – have been criticized publicly for referring to a black man as "boy."[5][6]

During an event promoting the 2017 boxing bout between Floyd Mayweather Jr. and Conor McGregor, the latter told the former to "dance for me, boy."[8] The remarks led several boxers – including Mayweather and Andre Ward – as well as multiple commentators to accuse McGregor of racism.[8][9][10][11]

Some boys defy traditional gender expectations. Gender-expansive[lower-alpha 1] and transgender boys can face bullying and pressure to conform to traditional expectations.[12] Some intersex children and some transgender children who were assigned female at birth may self-identify as boys.[13]

Human sex is determined at fertilization when the genetic sex of the zygote has been initialized by a sperm cell containing either an X or Y chromosome. If this sperm cell contains an X chromosome, it will coincide with the X chromosome of the ovum and a girl will develop. A sperm cell carrying a Y chromosome results in an XY combination, and a boy will develop.[14]

Armenian boys at play

In male embryos at six to seven weeks' gestation, "the expression of a gene on the Y chromosome induces changes that result in the development of the testes". At approximately nine weeks' gestation, the production of testosterone by a male embryo results in the development of the male reproductive system.[15]

Filipino boy

The male reproductive system includes both external and internal organs. The external organs include the penis, the scrotum, and the testicles (or testes). The penis is a cylindrical organ filled with spongy tissue. It is the organ used by boys to expel urine. The foreskin of some boys' penises is removed in a process known as circumcision. The scrotum is a loose sac of skin behind the penis which contains the testicles. Testicles are oval-shaped gonads. A boy generally possesses two testicles. Internal male reproductive organs include the vas deferens, the ejaculatory ducts, the urethra, the seminal vesicles, and the prostate gland.[16][17]

Puberty is the process by which children's bodies mature into adult bodies that are capable of reproduction. On average, boys begin puberty at ages 11–12 and complete puberty at ages 16–17.[18][19]

In boys, puberty begins with the enlargement of the testicles and scrotum. The penis also increases in size, and a boy develops pubic hair. A boy's testicles also begin making sperm. The release of semen, which contains sperm and other fluids, is called ejaculation.[20] During puberty, a boy's erect penis becomes capable of ejaculating semen and impregnating a female.[16][17] A boy's first ejaculation is an important milestone in his development.[21] On average, a boy's first ejaculation occurs at age 13.[22] Ejaculation sometimes occurs during sleep; this phenomenon is known as a nocturnal emission.[20]

When a boy reaches puberty, testosterone triggers the development of secondary sex characteristics. A boy's muscles increase in size and mass, his voice deepens, his bones lengthen, and the shape of his face and body changes.[23] The increased secretion of testosterone from the testicles during puberty causes the male secondary sexual characteristics to be manifested.[24] Male secondary sex characteristics include:

Adolescent boys in Uruguay

• Growth of body hair, including underarm, abdominal, chest, and pubic hair.[25][23]
• Growth of facial hair.[23]
• Enlargement of larynx (Adam's apple) and deepening of voice.[23][26]
• Increased stature; adult males are taller than adult females, on average.[23]
• Heavier skull and bone structure.[23]
• Increased muscle mass and strength.[23]
• Broadening of shoulders and chest; shoulders wider than hips.[27]
• Increased secretions of oil and sweat glands.[26]