Which term refers to the vowel sound [ə] commonly found in many English words?

The term that refers to the vowel sound [ə] is "schwa." This sound is characterized by its neutral, unstressed quality and is the most common vowel sound in English. It often appears in unstressed syllables in words such as "sofa," "banana," and "the." The schwa is essential in the study of English phonetics as it exemplifies how vowel sounds can vary in production depending on stress patterns within words.

Consonants are separate phonemes that are articulated with some constriction in the vocal tract, whereas diphthongs are complex vowel sounds that begin with one vowel sound and glide into another within the same syllable. The term accent refers to variations in pronunciation that can signify regional or social identity, rather than a specific vowel sound. Thus, "schwa" is the precise term that captures the essence of the [ə] sound.