A and an

'A' and 'an' function as the indefinite forms of the grammatical article in the English language and can also represent the number one. An is the older form (related to one, cognate to German ein; etc), now used before words starting with a vowel sound, regardless of whether the word begins with a vowel letter. Examples: a light-water reactor; an LWR; a sanitary sewer overflow; an SSO; a HEPA filter (because HEPA is pronounced as a word rather than as letters); a hypothesis; an hour; a ewe; a hero; a one-armed bandit; an heir; a unicorn.

Juncture loss

In a process called juncture loss, the n has wandered back and forth between words beginning with vowels over the history of the language, where sometimes it would be a nuncle and is now an uncle. The Oxford English Dictionary gives such examples as smot hym on the hede with a nege tool from 1448 for smote him on the head with an edge tool and a nox for an ox and a napple for an apple. Sometimes the change has been permanent. For example, a newt was once an ewt (earlier euft and eft), a nickname was once an eke-name, where eke means "extra" (as in eke out meaning "add to"), and in the other direction, "a napron" became "an apron" and "a naddre" became "an adder." "Napron" itself meant "little tablecloth" and is related to the word "napkin". An oft-cited but inaccurate example is an orange: despite what is often claimed, English never used a norange. Although the initial n was in fact lost through juncture loss, this happened before the word was borrowed in English (see orange (word)).

Discrimination between a and an

The form "an" is always prescribed before words beginning with a silent h, such as "honorable", "heir", "hour", and, in American English, "herb". Some British dialects (for example, Cockney) silence all initial h's (h-dropping) and so employ "an" all the time: e.g., "an 'elmet". Many British usage books, therefore, discount a usage which some Americans (amongst others) employ as being a derivative of the Cockney. The reason is that the indefinite article a is pronounced either of two ways: as a schwa, or as the letter itself is pronounced, "long a" (actually a diphthong, /eɪ/). Some words beginning with the letter h have the primary stress on the second or later syllable. Pronouncing a as a schwa can diminish the sound of the schwa and melt into the vowel. Pronouncing it as a "long a" does not do this, but as the pronunciation cannot be prescribed, the word is spelled the same for either. Hence an may be seen in such phrases as "an historic", "an heroic", or "an hôtel of excellence", which was the by-line in an advertisement in a New York City newspaper.

Merriam-Webster's Dictionary of English Usage is more descriptive than prescriptive, but it advises, "You choose the article that suits your own pronunciation." Theodore Bernstein gives the straight vowel-sound vs. consonant-sound explanation but allows that one should indeed say "an hotel" if they think hotel is pronounced otel.

Such was also the case for some other words which take the place of the article. "My" and "thy" became "mine" and "thine", as in "mine uncle". This usage is now obsolete.

The appearance of an or a in front of words beginning with h is not limited to stress. Sometimes there are historical roots as well. Words that may have had a route into English via French (where all h's are unpronounced) may have an to avoid an unusual pronunciation. Words that derived from German however would use a as the h's would be pronounced. There is even some suggestion that fashion may have had some influence. When England was ruled by a French aristocracy, the tradition may have been to exclusively use an, while when Britain was governed by a German-based monarchy the tide may have changed to a.

Further, some words starting with vowels may have a preceding a because they are pronounced as if beginning with an initial consonant. "Ewe" and "user" have a preceding a because they are pronounced with an initial y consonant sound. "One-armed bandit" and "one-sided argument" also have a preceding a because they are pronounced with an initial w consonant sound.

To add emphasis to a noun, the preceding indefinite article is often pronounced as a long a (just as the definite article would be pronounced as "thee" in such cases), whether or not the schwa, or even "an" would be the appropriate usage. In recent years, there has been a noticeable trend to pronouncing almost all indefinite articles in this way, especially in radio or television announcements or news-reading.

Representing the number one

In addition to serving as an article, a and an are also used as synonyms for the number one, as in "make a wish", "a hundred". An was originally an unstressed form of the number án 'one'.

A and an are also used to express a proportional relationship, such as "a dollar a day" or "$150 an ounce" or "A Mars a day helps you work, rest and play", although historically this use of "a" and "an" does not come from the same word as the articles.

The mathematically-minded might heed H. S. Wall's reminder that the statement "I have a son" does not necessarily imply that "I have exactly one son" or that "I have only sons". In other words, "The little words count." — H. S. Wall, Creative Mathematics.

See also

• The