欸

āi ㄞ

- (indicating response)
- (sadly sighing)

ǎi ㄞˇ

- (literary) to rebuke loudly
  Tw
- (literary) to sigh
  Tw

ēi ㄟ

- hey (used to draw attention)

éi ㄟˊ

- eh huh (used to express surprise)

ěi ㄟˇ

- hmm (used to express disapproval)

èi ㄟˋ

- yes (used to express agreement)

Sources