Can the word 'world' be used as an adjective?

Most adjectives end in -ly, so you could use the Word as worldly. It can be used to describe someone who has world experience. The global studies professor is worldly enough to teach this class with passion and knowledge

World can be an adjective:

He is the world champion. We are facing another world crisis

Most adjectives don't end in -ly, a lot of adverbs do.

Adjectives are the part of speech that modifies a noun. They are distinguished in English morphologically by one of several suffixes, such as -able, -ous, -er, and -est, or syntactically by position directly preceding a noun or nominal phrase.