Ms.

Ms., or Ms (UK usage), (pronounced [mɪz] or [məz]) is an honorific used with the last name or full name of a woman. Ms, like Mrs and Miss, is a contraction of the honorific "Mistress", which is the feminine of "Mister" or "Master". However, unlike Miss and Mrs., it does not presume the addressee's marital status. Ms. originated in the United States and was popularized in the 1970s. It is now the default form of address for business correspondence with a woman.

Etymology
Although it is usually believed to be a creation of modern feminism, Ms. was sporadically used as early as the 1700s. "Mistress", like Mister, did not originally bear reference to marital status. This changed as the contractions "Miss" and "Mrs." came into use, beginning in the 17th Century. The pronunciation mizz for Mrs. has long been colloquial in the American South and other areas.
The modern use of Ms. in preference to the traditional appellations was conceived by Sheila Michaels in 1961, upon seeing what might have been a typographical error on a copy of News & Letters.[1] Address-o-graph plates were difficult to repair and small, poor groups would not waste resources to correct minor mistakes. Michaels' roommate, Mary Hamilton (Congress of Racial Equality's first female Field Secretary in the South) had spoken to the Marxist-Humanist group in Detroit and been mailed a copy of their newsletter. Michaels "was looking for a title for a woman who did not 'belong' to a man" [2] She knew the separation of Miss and Mrs. had been recent, but one could not suggest that women call themselves Mistress with its louche connotations. Her efforts to promote use of a new honorific were ignored in the Civil Rights era, and seven years later in the nascent Women's Movement. Around 1971, in a lull during a WBAI-radio interview with The Feminists group, Michaels suggested the use of Ms. (having chosen a pronunciation current for both in Missouri, her home). A friend of Gloria Steinem's heard the interview and suggested it as a title for her new magazine, Ms.
The usage of Ms. was championed as non-sexist language beginning in the 1970s when women entered the white-collar workforce in large numbers. At that time, many women adopted Ms. to show solidarity with the feminist movement as well as to influence the attitudes of their male and female colleagues.

Usage

American
Ms. is widely used in the U.S., much more so than currently in the UK. In business correspondence, it is standard. The default use of Ms. is also championed by a number of etiquette writers, including Judith Martin (who ironically writes under the pen name Miss Manners).
Several public opponents of "non-sexist language," such as William Safire, were finally convinced that Ms. had earned a place in English by the case of Geraldine A. Ferraro. Ms. Ferraro, a United States vice presidential candidate in 1984, was a married woman who went by her birth surname rather than her husband's surname (Zaccaro). Safire pointed out that it would be equally incorrect to call her "Miss Ferraro" or "Mrs. Ferraro" — or to confuse the reader by calling her "Mrs. Zaccaro."

British
The Times (UK) states in its style guide that "Ms is nowadays fully acceptable when a woman wants to be called thus, or when it is not known for certain if she is Mrs or Miss."
The Guardian (UK) states in its style guide that: "We use whichever the woman in question prefers: with most women in public life (Ms Booth, Mrs May, Miss Widdecombe) that preference is well known; if you don't know, try to find out; if that proves impossible, use Ms."
Most women in the UK appear to still style themselves either "Miss" or "Mrs." However, in some circles the appellation is now standard, for instance in business — and where one may not know or find relevant the marital status of the woman so addressed.
Mrs is still in common use socially, especially by women who have taken their husband's family name—still the vast majority. British school children may also address female teachers as Miss regardless of marital status.

Further information
The rare plural of Ms. is Mses. However, Judith Martin advocates the use of the French "Mesdames" for addressing multiple women. It is not standard to use Ms. as a term of direct address; usually Ma'am will be used.[citation needed]
In other European languages, non-sexist usage in this regard usually amounts to using words more or less equivalent to Mrs. (madame, Fr.; señora, Es.; senhora, Pt.; signora, It.; Frau, De.; bean-uasal, Ga. and Gd.) for both married and unmarried women, and whether they take their husband's name or not. This makes sense as these are usually the direct feminine equivalents of the male counterparts (monsieur, Fr.; señor, Es.; senhor, Pt.; signore, It.; Herr, De.; máistir, Ga.; maighstir, Gd.), whereas the equivalent of Miss is a diminutive of the female equivalent (mademoiselle, Fr.; señorita, Es.; senhorita, Pt.; signorina, It.; Fräulein, De.; ógbhean-uasal, Ga.; maighdeann-uasal, Gd.).

Madam or ma'am is a title for a woman. It is derived from the French madame, the equivalent of Mrs. or Ms., and literally signifying "my lady." The plural of madam in this sense is mesdames. The French madame is in turn derived from the ancient Latin mea domina meaning honored mistress of the home (domus) [1

Madam is used in direct address, without the woman's name, for example when addressed by a stranger: May I help you, madam? In the United States, "Ma'am" is usually used, although some women may feel insulted when addressed as "ma'am" because it makes them feel old. The male equivalent is sir.

Miss can be used in direct address to a woman, for example, May I help you, Miss? By British tradition, Miss is often used by schoolchildren to address female teachers without using their name, regardless of marital status.
In some styles of etiquette, the eldest daughter of a family was addressed on paper simply as Miss Doe, with the younger daughters being addressed as Miss Jane Doe and Miss Rebecca Doe. In person, as in when making introductions, the styling would have been extended to unmarried cousins with the same surname.
In the American South, Miss is also traditionally used irrespective of marital status and added to a woman's first name in direct or indirect address, as Miss Ellen from Gone with the Wind or Miss Ellie from Dallas. This form was also used in upper class households in all English-speaking countries by servants to address or refer to the unmarried ladies of the household, and occasionally in family-run businesses in the same manner, though more commonly it was used to address servants if they were addressed by title at all; such usages are rare today.
In addition, in the United States, "Miss" is also used irrespective of marital status in another context: in reference to a woman's age. "Miss" is usually used to a address a 'younger' woman, ie. "Can I help you, Miss?" while "Ma'am" is used to address an 'elder' woman, "Can I help you, Ma'am?". This is why so many women find it difficult, or are offended, when they begin to be addressed as "Ma'am". They feel it means they are being told they are 'old', rather than seeing it as a term of respect.
Miss was formerly the default title for a businesswoman, but it has largely been replaced by Ms. in this context. It was (and to some extent remains) also a default title for celebrities, such as actresses (Miss Helen Hayes, Miss Amelia Earhart). Such default usage has also proved problematic; the poet Dorothy Parker was often referred to as Miss Parker, even though Parker was the name of her first husband and she herself preferred Mrs. Parker. Later in the century, the use of "Miss" or "Mrs" became a problem for the New York Times in referring to political candidate Geraldine Ferraro, a married woman who did not use her husband's surname, since Mrs has only been used with a woman's maiden name in limited circumstances. (See more at Mrs.) Current American etiquette states that Ms. is preferred for a woman who has kept her maiden name after marriage and in a business setting where one is not sure of how the woman wants to be addressed. While Miss can be used it is usually reserved for girls under eighteen.[1]
Another notable use of Miss is as the title of a beauty queen (given that in most pageants it is a requirement that contestants be unmarried), such as Miss America, Miss Universe, or Miss Congeniality.
Other languages, such as French, Spanish, Bulgarian, and Portuguese, have borrowed the English Miss to refer to the winner of a beauty pageant.
Miss can be used in the plural, as Misses. The usage The Misses Doe was often used in the United Kingdom to refer to unmarried sisters, but this usage is now largely obsolete.
In India, a female school teacher is usually addressed as "Miss". The "Miss" is usually postfixed such as "Shanti Miss" when referring to them in absence. All students rise and say in chorus "Good Morning Miss" when the teacher enters the class.

Formal address and protocol
In English-speaking countries, the wife of a foreign dignitary is called Madame (note final 'e') in direct address and formal correspondence, rather than the equivalent word in the person's native language (Señora, Frau etc.). However, in other contexts, it traditionally refers to the female head of a brothel.
After addressing her as "Your Majesty," it is proper to address The Queen of the United Kingdom as "Ma'am" for the remainder of the conversation.
Usage of "Ma'am" is common in the Southern United States. The Ascencion Parish Public Schools requires elementary school students to address female teachers as "Ma'am" or "Mrs./Ms./Miss (Family name)" [2].

In composed titles
Madam is also used as the equivalent of Mr. in composed titles, such as Madam Justice, Madam Speaker, Madam President. Most of these titles are usually used only in direct address, without the woman's last name: one would say President Smith, not Madam President Smith, even if one would address her to her face as Madam President.
However, the title Madam Justice is used in third-person reference: Madam Justice Louise Arbour, Madam Justice Arbour.
In the United States Supreme Court, rather than adopting the title Madam Justice for female justices, the title Mr. Justice was replaced simply by Justice. Likewise, female presidents of the Republic of Ireland have preferred to be addressed simply as President in direct address, rather than Madam President. Female judges of the High Court of Justice of England and Wales are titled Mrs. Justice rather than Madam Justice, regardless of marital status. However, District Judges are referred to as either Madam or Ma'am.

Military and police use
"Ma'am" is commonly used to address female officers of the rank of Inspector and above in British police forces and female Commissioned Officers and Warrant Officers in the British Armed Forces.
In the United States Armed Forces, "ma'am" (to rhyme with "ham") is used to address female commissioned officers and Warrant Officers. Marine recruits and Air Force trainees also address female non-commissioned officers as "ma'am."