be vs knock back

be and knock back both are verbs.

Word	Noun	Adjective	Verb	Adverb
be	No	No	Yes	No
knock back	No	No	Yes	No

As verbs, knock back is a hyponym of be; that is, knock back is a word with a more specific, narrower meaning than be:

Other hyponyms of be include put back, set back.

be (verb)	knock back (verb)
spend or use time	cost a certain amount
work in a specific place, with a specific subject, or in a specific function
have an existence, be extant
have life, be alive
form or compose
have the quality of being; (copula, used with an adjective or a predicate noun)
occupy a certain position or area; be somewhere
be identical to; be someone or something
be identical or equivalent to
represent, as of a character on stage
be priced at
to remain unmolested, undisturbed, or uninterrupted -- used only in infinitive form