Is an םlive a k’zayis?
The term k’zayis means the size of an olive, as an olive in Hebrew is a zayis. Practically though, there are a lot of differant size olives. The poskim say that a kzayis is about the size of an Isreali matchbox, or the size of a golfball. For more information on this there is a wonderful sefer called The Halachos of Kzayis, by R’ Pinchos Bodner shlit”a.