When i should use "워" or "와" if verb ends on "ㅂ"?
For example: 반가워요 // 도와요? Also i want to know if verb ends on "르" like this 부르다 then i change to 불러요, but if verb has patchim then how it will be (i do not know examples)? and one more question what i should use 어 or 아 if i have verb which ends on this vowels 와 워 위 의 외 애 얘 에 예 웨 왜?

Thanks a lot

Question

When i should use "워" or "와" if verb ends on "ㅂ"?
For example: 반가워요 // 도와요? Also i want to know if verb ends on "르" like this 부르다 then i change to 불러요, but if verb has patchim then how it will be (i do not know examples)? and one more question what i should use 어 or 아 if i have verb which ends on this vowels 와 워 위 의 외 애 얘 에 예 웨 왜?

Thanks a lot

Answer

와 is used only two words 돕다, 곱다.

ㅂirregular verb/adjective rule is:

When a word stem with final consonant ㅂ + a particle start with vowel, ㅂ changed 우 or 오.

* ㅂ => 오 (only with 아 vowel) => 와
돕다, 곱다.
돕(다) + 아요 => 도와요
곱(다) + 아요 => 고와요
돕(다) + 으면 => 도우면
곱(다) + 으면 => 고우면

* ㅂ => 우
어렵다, 쉽다, 덥다, 춥다, 귀엽다, 입다, 아름답다, 맵다, 눕다, 줍다.
덥(다) + 어요 => 더워요

NB. 입다, 잡다, 씹다, 좁다, 넓다, 뽑다, 접다 are not ㅂirregular verb/adjective

* 르 Irregular Verbs
If a verb stem ending with 르 conjugate with a vowel particle like ~아/어 then 르 is changed into ㄹ라.
verbs like 가르다, 고르다, 기르다, 나르다, 모르다, 오르다, 찌르다, 흐르다, 다르다
모르(다) + ~아/어 => 모 + ㄹ + 라 => 몰라
고르(다) + ~아/어 => 고 + ㄹ + 라 => 골라

아 is used when the verb ends with ㅏ, ㅑ, ㅗ, ㅘ.
어 is used when the verb ends with the other vowels like ㅓ, ㅕ, ㅜ, ㅡ, ㅣ, ㅐ, ㅔ, ㅖ, ㅞ, ㅚ, ㅟ, ㅢ ...

Answer

If the vowel in the syllable before is ㅗ or ㅣ you use .ㅏ Otherwise, you use ㅓ. However, you will form contractions without pachim

There is more detailed discussion of it here: https://funkorean4u.wordpress.com/2014/04/28/present-tense-verb-ending-%EC%95%84%EC%9A%94%EC%96%B4%EC%9A%94%EC%97%AC%EC%9A%94/