agree vs underpin

agree and underpin both are verbs.

Word	Noun	Adjective	Verb	Adverb
agree	No	No	Yes	No
underpin	No	No	Yes	No

As verbs, underpin is a hyponym of agree; that is, underpin is a word with a more specific, narrower meaning than agree:

agree: be compatible, similar or consistent; coincide in their characteristics
underpin: support with evidence or authority or make more certain or confirm

agree (verb)	underpin (verb)
be in accord; be in agreement	support from beneath
consent or assent to a condition, or agree to do something	support with evidence or authority or make more certain or confirm
achieve harmony of opinion, feeling, or purpose
be agreeable or suitable
be compatible, similar or consistent; coincide in their characteristics
go together
show grammatical agreement