constrain vs tie down

constrain and tie down both are verbs.

Word	Noun	Adjective	Verb	Adverb
constrain	No	No	Yes	No
tie down	No	No	Yes	No

As verbs, tie down is a hyponym of constrain; that is, tie down is a word with a more specific, narrower meaning than constrain:

constrain: to close within bounds, or otherwise limit or deprive of free movement
tie down: secure with or as if with ropes

Other hyponyms of constrain include bind, tie up, truss, fetter, shackle, enchain, pinion, shackle, impound, pound, pound, pound up, fold, pen up, ground.

constrain (verb)	tie down (verb)
severely restrict in scope or extent	restrain from independence by an obligation
to close within bounds, or otherwise limit or deprive of free movement	secure with or as if with ropes
compel to behave in a certain way