informant vs speaker

informant and speaker both are nouns.

Word	Noun	Adjective	Verb	Adverb
informant	Yes	No	No	No
speaker	Yes	No	No	No

As nouns, speaker is a hypernym of informant; that is, speaker is a word with a broader meaning than informant:

informant: someone who sees an event and reports what happened
speaker: someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)

Other hypernyms of informant include beholder, observer, perceiver, percipient, talker, utterer, verbaliser, verbalizer.

informant (noun)	speaker (noun)
a person who supplies information	electro-acoustic transducer that converts electrical signals into sounds loud enough to be heard at a distance
someone who sees an event and reports what happened	someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)