constrain vs ground

constrain is not a noun while ground is a noun.

Word	Noun	Adjective	Verb	Adverb
constrain	No	No	Yes	No
ground	Yes	No	Yes	No

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

constrain: to close within bounds, or otherwise limit or deprive of free movement
ground: confine or restrict to the ground

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

constrain (noun)	ground (noun)
	the first or preliminary coat of paint or size applied to a surface
	(art) the surface (as a wall or canvas) prepared to take the paint for a painting
	a connection between an electrical device and a large conducting body, such as the earth (which is taken to be at zero voltage)
	the part of a scene (or picture) that lies behind objects in the foreground
	a relatively homogeneous percept extending back of the figure on which attention is focused
	a position to be won or defended in battle (or as if in battle)
	a rational motive for a belief or action
	the solid part of the earth's surface
	material in the top layer of the surface of the earth in which plants can grow (especially with reference to its quality or use)
	a relation that provides the foundation for something
	the loose soft material that makes up a large part of the land surface

constrain (verb)	ground (verb)
severely restrict in scope or extent	use as a basis for; found on
to close within bounds, or otherwise limit or deprive of free movement	instruct someone in the fundamentals of a subject
compel to behave in a certain way	place or put on the ground
	confine or restrict to the ground
	connect to a ground
	cover with a primer; apply a primer to
	fix firmly and stably
	(baseball) a hit that travels along the playing field.
	throw to the ground in order to stop play and avoid being tackled behind the line of scrimmage
	hit or reach the ground
	bring to the ground