Linguistics 101—Speaking in ‘Schwa’
What is the most commonly used vowel sound in the English language? You might quibble over ‘a’, ‘e’, or ‘i’, but to find the answer you have to look beyond the five commonly accepted vowels (or six if you include ‘y’) to a little-known vocal utterance called schwa.
Schwa is defined as the toneless, neutral vowel sound found in the unstressed part of a word. The ‘e’ in happen is an example of schwa, as is the ‘a’ in affect (which could be why affect and effect are so commonly mixed up). The International Phonetic Alphabet writes schwa as ə, like an e that came to a stop halfway through a somersault (the ‘e’ in somersault is a schwa, by the way).
So any vowel sound that comes out as ah, eh or uh is more than just slacker speak; it’s a legitimate part of the spoken language.