The schwa sound is a mid-central, neutral vowel sound that is commonly found in unstressed syllables in the English language, such as the 'a' in 'balloon' or the 'u' in 'circus'. In other languages, the schwa might be used for stressed vowels or for other unstressed and toneless neutral vowels.
The "schwa" is represented by a symbol resembling the letter "e" rotated 180 degrees. The name itself is German and originates from the Hebrew word "shewa," which means "a neutral vowel quality," or more literally, "emptiness."
In phonetics, the schwa is a monophthong, which is a pure vowel sound that retains a relatively fixed articulation at the beginning and end of a single syllable.