ADVERB generally corresponds to an ADJECTIVE. REGULAR adverbs are simply formed by adding “-ly” or other changes. IRREGULAR adverbs, on the other hand, are not formed from standard English spelling conventions (not always use “by”). You have to memorize them or find on Dictionary. BUT, we can simply identify the both from the position in sentence by knowing adjective or adverb. Eg. Regular Arverb She is a beautiful singer. (Ajdective) She sings a song beautifully. (Adverb) Eg. Irregular Adverb He is a fast runner. (Adjective) He runs fast. (Adverb) Either regular or irregular adverb, with suffix-ly or other changes above, means commonly in Bahasa Indonesia as “dengan/secara”