dike vs weir

dike and weir both are nouns.

Word	Noun	Adjective	Verb	Adverb
dike	Yes	No	Yes	No
weir	Yes	No	No	No

As nouns, weir is a hyponym of dike; that is, weir is a word with a more specific, narrower meaning than dike:

dike: a barrier constructed to contain the flow of water or to keep out the sea
weir: a low dam built across a stream to raise its level or divert its flow

Other hyponyms of dike include milldam.

dike (noun)	weir (noun)
a barrier constructed to contain the flow of water or to keep out the sea	a low dam built across a stream to raise its level or divert its flow
(slang) offensive term for a lesbian who is noticeably masculine	a fence or wattle built across a stream to catch or retain fish

dike (verb)	weir (verb)
enclose with a dike