spirant vs sibilant

spirant and sibilant both are nouns.

Word	Noun	Adjective	Verb	Adverb
spirant	Yes	Yes	No	No
sibilant	Yes	Yes	No	No

As adjectives, spirant and sibilant are synonyms defined as:

spirant and sibilant: of speech sounds produced by forcing air through a constricted passage (as `f', `s', `z', or `th' in both `thin' and `then')

Other synonyms of spirant include continuant, fricative, strident.

As nouns, sibilant is a hyponym of spirant; that is, sibilant is a word with a more specific, narrower meaning than spirant:

spirant: a continuant consonant produced by breath moving against a narrowing of the vocal tract
sibilant: a consonant characterized by a hissing sound (like s or sh)

Other hyponyms of spirant include sibilant consonant.

spirant (noun)	sibilant (noun)
a continuant consonant produced by breath moving against a narrowing of the vocal tract	a consonant characterized by a hissing sound (like s or sh)

spirant (adjective)	sibilant (adjective)
of speech sounds produced by forcing air through a constricted passage (as `f', `s', `z', or `th' in both `thin' and `then')	of speech sounds produced by forcing air through a constricted passage (as `f', `s', `z', or `th' in both `thin' and `then')