There are some verbs that have vowel contracts when they are conjugated in the standard polite form.

For example, 오다 (to come)is conjugated as 와요 in the standard polite form.

There are lots of verbs that contain 오다 :

따라오다 – to follow along

들어오다 – to come in

데려오다 – to bring someone along

And these are just a few of the many more that contain 오다.

언제 집에 들어왔어요? = When did you come home?

(언제 = when. 집 = home. 에 = location marker. 들어왔어요 = past tense of “come”)

Like 오다, 보다 will have a change in the vowel :

영화를 봤어요 = I watched a movie

(영화 = movie. 를 = object marker. 봤어요 = watched)

Like 오다, the vowel in 보다 changed to 봐.

There’s another type of verb that changes when conjugated in the standard polite form :

Depending on the context, 치다 can mean “to play”, “to take a test”, or “to strike”, in addition to other meanings.

린다는 피아노를 쳐요 = Linda plays the piano

(린다 = Linda. 는 = topic marker. 피아노 = piano. 를 = object marker. 쳐요 = play)

The vowel in 치다 changes to 쳐.

Other verbs contain 치다 like :

가르치다 = to teach

그치다 = to stop, cease

넘치다 = to overflow