A woman is a female human being (specifically an adult, a female child is a girl), as contrasted to a man, an adult male (as a child, boy). The terms woman (irregular plural: women) and girl are used to indicate biological sex distinctions, cultural gender role distinctions, or both.
The term "man" (from Proto-Germanic mannaz "man, person") and words derived from can designate any or even all of the human race regardless of their gender or age. This is indeed the oldest usage of "man". In Old English the words wer and wyf (also wæpman and wifman ) were what was used to refer to "a man" and "a woman" respectively, and "man" was gender neutral. In Middle English man displaced wer as term for "male human," whilst wyfman (which eventually evolved into woman) was retained for "female human." Man does continue to carry its original sense of "Human" however, resulting in an asymmetry sometimes criticized as sexist. 
Biology and sex
Biological factors are not the determinant of whether persons are considered (or considers themselves) women; some women can have abnormal hormonal or chromosomal differences (such as congenital adrenal hyperplasia or other intersex conditions), and there are women without typical female physiology (trans, transgendered or transsexual women). (See gender identity.)
In terms of biology, females have various sexual characteristics that differentiate them from men. In women, the sex organs are involved in the reproductive system, whereas the secondary sex characteristics are involved in attracting a mate or nurturing children. Most non-transexual women have the karyotype 46,XX, but around one in a thousand will be 47,XXX and one in 2500 will be 45,X.
Although fewer females than males are born (the ratio is around 1:1.05), women make up the majority of the adult population. This is because males of all ages have a slightly higher death rate (even in the womb) and women live, on average, five years longer than men. This is thought to be a result of a combination of factors: genetics (redundant and varied genes present on sex chromosomes in women); sociology (such as military service); health-impacting choices (such as suicide or the use of cigarettes and alcohol); the presence of the female hormone estrogen, which has a cardioprotective effect in premenopausal women; and the effect of high levels of androgens in men.
After the onset of menarche, most women are able to become pregnant and bear children. The study of female reproduction and reproductive organs is called gynaecology. Women generally reach menopause in their late 40s or early 50s, at which point their ovaries cease producing estrogen and they can no longer become pregnant.
In general, women suffer from the same illnesses as men; however there are some sex-related illnesses that are found more commonly or exclusively in women.
Legal rights of women historically
See article legal rights of women.
The dependent position of women in early law is proved by the evidence of most ancient systems of early law which have in whole or in part descended to us. In the Mosaic law divorce was a privilege of the husband only, the vow of a woman might be disallowed by her father or husband, and daughters could inherit only in the absence of sons, and then they must marry in their tribe. The guilt or innocence of a wife accused of adultery might be tried by the ordeal of the bitter water. Besides these instances, which illustrate the [2 Deut. xxiv. 1. Numb. xxx. 3-Numb. xxvii., xxxvi. Numb. v. II.] subordination of women, there was much legislation dealing with, inter alia, offences against chastity, and marriage of a man with a captive heathen woman or with a purchased slave. So far from second marriages being restrained, as they were by Christian legislation, it was the duty of a childless widow to marry her deceased husband's brother.
Culture and gender roles
Main article: gender role
From prehistory, women, like men, have assumed a special cultural role. In hunter-gatherer societies, women have almost always been the gatherers of plant foods which have provided the great majority of the diet, while men have hunted meat. Because of their intimate knowledge of plant life, most anthropolgists think it was women who led the Neolithic Revolution and became history's first pioneers of agriculture.
In more recent history, the gender roles of women have changed greatly. Traditional gender roles for middle-class women typically involved domestic tasks emphasizing child care, and did not involve entering employment for wages. For poorer women, especially among the working classes, this often remained an ideal, for economic necessity has long compelled them to seek employment outside the home, although the occupations traditionally open to working-class women were lower in prestige and pay than those open to men. Eventually, restricting women from wage labor came to be a mark of wealth and prestige in a family, while the presence of working women came to mark a household as being lower-class.
The women's movement is essentially a struggle for the recognition of equality of opportunity with men, and for equal rights irrespective of sex, even if special relations and conditions are willingly incurred under the form of partnership involved in marriage. The difficulties of obtaining this recognition are obviously due to historical causes combined with the habits and customs which history has produced. Through a combination of economic changes and the efforts of the feminist movement in recent decades, however, women in most societies now have access to careers beyond the traditional one of "homemaker".
These changes are among the foci of the academic field of women's studies.
The English language's original word for "woman" was Old English wīf, akin to German Weib; it later became the modern word "wife." The modern word "woman" etymologically derives from wīfmann, with the addition of mann, "person", from Germanic mannaz. This formation is peculiar to English. The equivalents for "man" in Old English were wer (a cognate of Latin vir, "man") and wǣpnedmann, literally "weaponed person", where "weapon" is used as a euphemism for "penis".
The word girl originally meant "young person of either sex"; it was only around the beginning of the 16th century that it came to mean specifically a female child. Nowadays girl is also often used colloquially to refer to a young or unmarried woman. Since the early 1970s, feminists have challenged such usage, and today, using the word in the workplace (as in office girl) is typically considered inappropriate in the United States because it implies a view of women as infantile. The use remains commonplace in several other English-speaking countries.
Conversely, in certain non-Western cultures which link family honor with female virginity, the word girl is still used to refer to a never-married woman; in this sense it is used in a fashion roughly analogous to the obsolete English maid or maiden. Referring to an unmarried female as woman can, in such a culture, imply that she is sexually experienced, which would be an insult to her family.
In more informal settings, the use of girl to refer to an adult female is also common practice in certain usage (such as girls' night out), even among elderly women. In this sense, girl may be considered to be the analogue to guy or bloke for a man (the latter being rare in American English). Some regard non-parallel usages, such as men and girls, as offensive.
There are also many slang terms to refer to women; these have existed throughout history, and change over time. Some of those common in contemporary usage are:
Bird: primarily a Britishism, some women see it as demeaning. Others celebrate it with events such as "hen parties".
Chick: literally a young chicken or (more broadly) a young bird of any kind, this term is mildly offensive to some women who understand it as infantalizing or objectifying; it is chiefly an Americanism. It is sometimes claimed that the usage derives from the Spanish chica (girl), but neither the Oxford English Dictionary nor Merriam-Webster supports this derivation. (The word chick was used in a gender-neutral sense to mean "human child" at least as early as the fourteenth century.) The popularity of the usage in North America may, nonetheless, be due in part to its similarity to the Spanish word.
Sister: a term which women rarely use when addressing each other; it is associated with, although by no means exclusive to, African American idiom. The same term is used within feminism, and also in the transsexual community in referring to other transsexuals.
- Sheila: commonly used in Australia.
Several older, mildly pejorative terms which men formerly employed for women in general, such as broad or skirt, are now archaic, and rarely encountered.
Authors often create new euphemisms or other terms to refer to women, an example being the use of the word burger on the American television sitcom The Cosby Show to refer to an attractive female. Science fiction fandom has also adapted terms from literature, film, and television.
In some cultural groups, terms considered extremely offensive to most women (e.g., bitch, cunt, or ho) are used to refer to women in general. Many terms which refer to women's physical appearance (e.g., hottie, a sexually-attractive woman) see wide use, but many consider them to imply sexual objectification, although many heterosexual women use hunk to describe an equivalent man.