sob vs tears

sob and tears both are nouns.

Word	Noun	Adjective	Verb	Adverb
sob	Yes	No	Yes	No
tears	Yes	No	No	No

As nouns, tears is a hypernym of sob; that is, tears is a word with a broader meaning than sob:

sob: convulsive gasp made while weeping
tears: the process of shedding tears (usually accompanied by sobs or other inarticulate sounds)

Other hypernyms of sob include crying, weeping.

sob (noun)	tears (noun)
convulsive gasp made while weeping	the process of shedding tears (usually accompanied by sobs or other inarticulate sounds)

sob (verb)	tears (verb)
weep convulsively