Schwa
From Citizendium, the Citizens' Compendium
Schwa[1] is the name linguists use for the most neutral of vowel sounds, the usual, weak, pronunciation of the indefinite article 'a', the gentle grunt of 'uh huh'. Its phonetic symbol is [ə].
In English, it can be represented by a number of vowel-letters: it is the u in careful, the e in worker, the a in above and the o in person.
Some languages have more than one schwa. In addition to the English one, Portuguese has [ɐ], which, as its 'a'-like symbol implies, is a little more open.
Russian final o is pronounced schwa, a fact almost never reflected in English.
The name is derived from a Hebrew word that means "emptiness" or "vanity," and it is also the name of a Hebrew vowel mark that is sometimes pronounced like a schwa, and sometimes not pronounced at all.[2]
