The French prefix ci- can be added to various parts of speech to indicate the location or inclusion of something mentioned in a document (ci-joint, ci-inclus...)
The French prefix là- can be added to nine adverbs, mostly adverbs of place, to indicate location.
Adjectives comprise one of the eight French parts of speech, but certain members of other grammatical categories can sometimes be used as adjectives. These "non-adjectives" are invariable: there's no gender/number agreement with the nouns they modify.
The French prefix re- can be added to hundreds of verbs to make new verbs. Depending on the first letter of the verb it's added to, re- has a few variations as well as some different meanings.