izmena

1. change; modification; amendment
   Napravili smo nekoliko izmena u tekstu. — We made a few changes to the text.
   Od ponedeljka važe izmene u redu vožnje. — The timetable changes take effect on Monday.
2. (in sports) substitution
   Trener je u drugom poluvremenu napravio dve izmene. — The coach made two substitutions in the second half.
3. alternation; succession
   Izmena dana i noći zavisi od rotacije Zemlje. — The alternation of day and night depends on the Earth's rotation.

Izmena usually means a partial alteration of something existing; promena is the broader word.