Lesson 145: Yarı - yarım
Yarım is an irregular word. It corresponds to half or semi in English. However, the m is dropped when you use yarım in the following situations.
Before adjectives: yarı açık (half-open)
In compounds: elmanın yarısı (half of the apple)
In the adverbial phrase: yarı yarıya (fifty-fifty)
In other cases, it is yarım, including the m.