dreamer vs daydreamer

dreamer and daydreamer both are nouns.

Word	Noun	Adjective	Verb	Adverb
dreamer	Yes	No	No	No
daydreamer	Yes	No	No	No

As nouns, daydreamer is a hypernym of dreamer; that is, daydreamer is a word with a broader meaning than dreamer:

Other hypernyms of dreamer include woolgatherer.

dreamer (noun)	daydreamer (noun)
a person who escapes into a world of fantasy	someone who indulges in idle or absentminded daydreaming
someone guided more by ideals than by practical considerations
someone who is dreaming