이나 after a consonant (책이나), 나 after a vowel (커피나)
or; … or something; as many as
Example
이번 주말에 같이 영화나 볼까요?
Shall we watch a movie or something this weekend?
Good to know
With numbers it shows surprise: 세 시간이나 기다렸어요 'I waited a whole three hours.'
Related words