hoary vs grey-headed

hoary and grey-headed both are adjectives.

Word	Noun	Adjective	Verb	Adverb
hoary	No	Yes	No	No
grey-headed	No	Yes	No	No

As adjectives, hoary and grey-headed are synonyms defined as:

hoary and grey-headed: showing characteristics of age, especially having grey or white hair

Other synonyms of hoary include gray-haired, gray-headed, gray, grey-haired, grey, grizzly, hoar, white-haired.

hoary (adjective)	grey-headed (adjective)
covered with fine whitish hairs or down	showing characteristics of age, especially having grey or white hair
ancient
showing characteristics of age, especially having grey or white hair