-n is added to words ending in a vowel. Final -a changes to -á-. Final -e changes to -é-.
-an is added to most back-vowel words ending in a consonant
-on is added to some back-vowel words ending in a consonant
-en is added to front-vowel words ending in a consonant, as well as some front-vowel words ending in a vowel. Their original word-final vowel may be lost (e.g. könnyű) or supplemented with a consonant (e.g. bő, hű).
(denumeral and depronominal adverb-forming suffix) Variants:
-n is added to some (very few) words ending in a vowel. Final -a changes to -á-. Final -e changes to -é-.
-an is added to back-vowel words ending in a consonant
-en is added to front-vowel words ending in a consonant, as well as some front-vowel words ending in a vowel. Their original word-final vowel may be lost (e.g. kettő).