I am wondering why the infinitive verb 모르다 (do not know) is conjugated as 몰라요 in informal style and standard politeness?
모르다 is an irregular verb because the base form 모르 ends with ㅡ so the vowel ㅡ is dropped when followed by vowels (examples: -아/어/여) and after dropping ㅡ, one of -아/어/여 has to be chosen according to the vowel in the previous syllable.
So if we follow the grammatical rule it should be 모르다 -> 모라요.
How come we add an extra 리을 (ㄹ) to get 몰라요 when we conjugate 모르다 in informal style, standard politeness?
Is it another exception because it's easier for the pronunciation because 몰라요 is pronounced "Mol-la-yo"?