phoneme

Concise Oxford English Dictionary © 2008 Oxford University Press:
phoneme /ˈfəʊniːm/

▶noun Phonetics any of the distinct units of sound that distinguish one word from another, e.g. p, b, d, and t in pad, pat, bad, and bat.

– derivatives
phonemic /-ˈniːmɪk/ adjective,
phonemics plural noun.

– origin C19: from Fr. phonème, from Gk phōnēma ‘sound, speech’, from phōnein ‘speak’.