Compound adjectives: gray-haired, student-centered, etc.

[Pdarlyn1]

hi everybody
i have difficulties with words like these;gray-haired,student -centered.are they compound words? can somebody tell me how and when to use this sort of word.
thanks.

best regards

[Cerberus™]

Yes, they are compound adjectives. A gray-haired person is someone who has gray hair. A student-centered program is a program that is centered on students.

[Anna.ha]

There is a common rule to create this kind of compound adjectives: adjective + dash + noun + ed, e.g
He is a bald-headed person.
He is a left-handed person.
...

And also another rule to form a compound adjective: adverb + verb + ed, e.g

This is a commonly used expression.
This is a locally used application.

Am i correct?

[Cerberus™]

Yes, although I'd usually not call adverb+participle or adverb+adjective compound adjectives: I'd say they are seperate words in an ordinary construction, that of the adverb modifying the participle or adjective.

In special cases you might need to add a hyphen against ambiguity, though. For example when a word may be either adjective or adverb in the same form: "a fast-decreasing speed" vs. "a fast decreasing speed". In the first "fast" is an adverb modifying "decreasing", in the second an adjective modifying "speed". There exists no adverb *fastly. This example is perhaps not very realistic but I hope you get my point.