The Greek adverbs derive from the adjectives.

How to form Greek adverbs:

adjective stem + -α or -ως ending

Comparative/Superlative of adverbs

The comparative is formed by the ending -ότερα or by the word πιο located before the adverb.

Besides there are numerous adverbs with adverbial phrases which are not directly derived by/from an adjective.

• The local adverb points to a location, such as εδώ (here), πουθενά (nowhere, παντού (everywhere), εκεί (there), μέσα (inside), έξω (outside), μπροστά (upfront), πίσω (behind)
• The causal adverb points to a cause, such as επειδή, γιατί (because/since), μολονότι (although/despite), παρόλα αυτά (nevertheless), γι’αυτό (therefore), γιατί (namely)
• The temporal adverb points to notions of time, such as χθες (yesterday), σήμερα (today), τώρα (now), αύριο (tomorrow), φέτος (this year), πέρυσι (last year)
• The modal adverb points to the way of doing something, such as πραγματικά (really), φυσικά/βέβαια/βεβαίως (naturally), σκόπιμα/επίτηδες (intentionally/purposely), έτσι (this way), καθόλου (not at all)