thermos flask vs vacuum bottle

thermos flask and vacuum bottle both are nouns.

Word	Noun	Adjective	Verb	Adverb
thermos flask	Yes	No	No	No
vacuum bottle	Yes	No	No	No

As nouns, vacuum bottle is a hypernym of thermos flask; that is, vacuum bottle is a word with a broader meaning than thermos flask:

thermos flask: vacuum flask that preserves temperature of hot or cold drinks
vacuum bottle: flask with double walls separated by vacuum; used to maintain substances at high or low temperatures

Other hypernyms of thermos flask include vacuum flask.

thermos flask (noun)	vacuum bottle (noun)
vacuum flask that preserves temperature of hot or cold drinks	flask with double walls separated by vacuum; used to maintain substances at high or low temperatures