consonant: one of the two great classes of linguistic sounds, the other being the vowels. The formation of consonants involves greater constriction of the moving airstream than for vowels, often resulting in either friction (which produces a "hissing" noise) or complete stoppage of the air. Consequently, they usually have less sonority than vowels. They generally function at the beginning and/or end of syllables, while vowels serve as the center or "nucleus" of a syllable. The capital letter C is often used to mean 'consonant'. (See the diagram of phonetic symbols for consonants.) [Spanish: consonante]