understand vs realize

understand and realize both are verbs.

Word	Noun	Adjective	Verb	Adverb
understand	No	No	Yes	No
realize	No	No	Yes	No

As verbs, understand and realize are synonyms defined as:

Other synonyms of understand include realise, see.

understand (verb)	realize (verb)
know and comprehend the nature or meaning of	perceive (an idea or situation) mentally
perceive (an idea or situation) mentally	be fully aware or cognizant of
believe to be the case	make real or concrete; give reality or substance to
make sense of a language	expand or complete (a part in a piece of baroque music) by supplying the harmonies indicated in the figured bass
be understanding of	convert into cash; of goods and property
	earn on some commercial or business transaction; earn as salary or wages