part-of-speech tagger vs tagger

part-of-speech tagger and tagger both are nouns.

Word	Noun	Adjective	Verb	Adverb
part-of-speech tagger	Yes	No	No	No
tagger	Yes	No	No	No

As nouns, tagger is a hypernym of part-of-speech tagger; that is, tagger is a word with a broader meaning than part-of-speech tagger:

part-of-speech tagger: a tagging program whose labels indicate a word's part of speech
tagger: a computer program that attaches labels to the grammatical constituents of textual matter

Other hypernyms of part-of-speech tagger include tagging program.

part-of-speech tagger (noun)	tagger (noun)
a tagging program whose labels indicate a word's part of speech	a computer program that attaches labels to the grammatical constituents of textual matter
	someone who appends or joins one thing to another
	someone who assigns labels to the grammatical constituents of textual matter