head off vs ward off

head off and ward off both are verbs.

Word	Noun	Adjective	Verb	Adverb
head off	No	No	Yes	No
ward off	No	No	Yes	No

As verbs, head off and ward off are synonyms defined as:

head off and ward off: prevent the occurrence of; prevent from happening; to protect from or to keep away anything undesirable; to ward off

Other synonyms of head off include avert, avoid, debar, deflect, fend off, forefend, forfend, obviate, stave off.

head off (verb)	ward off (verb)
prevent the occurrence of; prevent from happening; to protect from or to keep away anything undesirable; to ward off	avert, turn away, or repel
	prevent the occurrence of; prevent from happening; to protect from or to keep away anything undesirable; to ward off