✔ 最佳答案
In fact, these are called 'adverbs', which are words that modifies the verb. Adjectives are words that describe or modifies the object/ noun in a sentence.
eg. A fast cat - 'fast' is an adjective
eg. The cat moves quickly - 'quickly' is an adverb (think 'add to verb = adverb)
Back to the question - there are many exceptions in English, and this is one of them. While most adverbs simply add '-ly' ending, these are the exceptions with words ending with 'e':
truly (true), wholly (whole), duly (due)
There are also other rules, such as -
'y' ending - remove 'y', add '-ily'; eg. happy - happily
'le' ending - remove 'e', add '-y'; eg. terrible - terribly
'ic' ending - add '-ally'; eg. ironic - ironically
Hope that helps