Schwa is the most common vowel sound in English, even though most people have never heard of it. It's the lazy, unstressed “uh” sound that appears in words like about, problem, circus, and banana. Say those words naturally and notice how some vowels get reduced to a quick, neutral “uh”: uh-BOUT, PROB-luhm, CIR-kuhs, buh-NAN-uh.

The schwa appears in dictionaries with this symbol: ə. It shows up whenever a vowel becomes unstressed and relaxed in normal speech. The same letter can make different sounds depending on whether it's stressed: compare the a in America (“uh-MAIR-ih-kuh”), where the first a is a schwa but the second is a clear “AIR” sound.

Understanding schwa helps explain why English spelling seems so inconsistent. The vowels in lemon, pencil, and doctor all make the same schwa sound in their second syllables, even though they're spelled with different letters. Your mouth naturally wants to make this neutral sound when quickly moving between stressed syllables.