fricative vs sibilant

fricative and sibilant both are nouns.

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

As adjectives, fricative and sibilant are synonyms defined as:

fricative 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 fricative include continuant, spirant, strident.

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

fricative: 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 fricative include sibilant consonant.

fricative (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)

fricative (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')