3,310. Combining to Form a K'zayis

Terumos 10:4

The following things all combine to make up the volume of an olive in order to render one liable for death from Heaven or to repay adding a fifth: terumah, terumas maaser – whether from doubtfully tithed or definitely untithed produce, challah and first fruits. This is because all of these things are called “terumah” by the Torah. Really, one shouldn’t be liable for the extra fifth for eating doubtfully tithed terumas maaser, the same as one is not liable for doubtfully tithed maaser sheini (second tithe), but the Sages said that if people aren’t liable for the extra fifth, they will treat it lightly.

Terumos 10:5

If someone ate terumah intentionally after being warned, he is liable to the penalty of lashes and he need not repay the misappropriation. If he wasn’t warned, he must repay. If the terumah was ritually clean, he must repay what he ate, but he need not add the extra fifth. If it was ritually unclean, he need only repay the value of wood because it’s only fit for use as fuel. Therefore, if someone ate berries or pomegranates that were ritually unclean terumah, he need not repay because they are unfit for use as fuel.