cf. principle 45.
MBG writes: “The line of distinction between adverbs and other forms of speech can often be difficult to draw. For example, is μόνον the accusative neuter of μόνος functioning adverbially, or has it become set as an adverb? If not μόνον, then how about πρῶτον or ὕστερον?” p242
1. Most adverbs are formed from adjectives and end in -ως.
δικαιος – just (adj) δικαιως – justly (adv);
αληθης – true (adj) αληθως – truly (adv);
2. The accusative of an adjective (neuter) or noun may be used as an adverb.
3. While most adverbs end in -ως, some also end in -θεν, θι, and δε.
ουρανοθεν – from heaven (Acts 14:17)
παιδιοθεν – from childhood (Mark 9:21)
περουσι – last year (2Cor. 8:10)
ενθαδε – here, hither (Acts 10:18)
4. Numeral adverbs generally end in -ις, -κις, and -ακις.
δις – twice
τρις – three times
επτακις – seven times
πολλακις – many times
εβδομηκοντακις – seventy times
5. Some adverbs are formed from verbs; others from prepositions.
δευρο adv. meaning “hither” comes from the verb δευτε meaning “come here”.
There are not many direct adverbs in Biblical Hebrew, other kinds of words often function as adverbs. source