나

or — between nouns (after a vowel)

Offers two nouns as alternatives: 영화나 시리즈 'movies or series', 선풍기나 에어컨 'a fan or an air conditioner', 허리나 다리 'the back or the legs'. After a consonant the same particle is written 이나. The very common X나 이런 거 means 'X and things like that', naming one example instead of listing everything. To connect actions rather than nouns you need 거나 instead (듣거나 보거나).

Register: neutral, extremely common in speech