Regular Adverbs
From TEFL World Wiki
Regular adverbs are those adverbs that are formed by adding -ly to an adjective. This addition usually causes no changes in the word and it is a simple matter of placing -ly at the end of the adjective.
slow > slowly
loud > loudly
great > greatly
perfect > perfectly
sincere > sincerely
However there are some cases where a few changes take place.
1. the adjective ends in -y in which case the -y changes into -i before -ly is added
speedy > speedily
angry > angrily
ready > readily
2. the adjective ends in -able, -ible, or -le in which case the -e changes into -y
gentle > gently
humble > humbly
probable > probably
3. the adjective ends in -ic in which case simply add -ally
economic > economically
basic > basically
ergonomic > ergonomically
Exception: public > publicly, and not * publically.
