Terumos 2:4-5

Terumos 2:4

One may not take terumah from one type of produce for another type; if one did so, he has accomplished nothing. All types of wheat count as one type. All types of figs, dried figs and cakes of pressed figs are one type, so one make take terumah from one for the other. If there is a kohein to whom to give the terumah, the owner must take it from the best kind of produce (e.g., from the fresh figs for the dried figs) but when there is no kohein, he takes from the type that will last (e.g., from the dried figs for the fresh figs). Rabbi Yehuda says that one must always take terumah from the best type of produce.

Terumos 2:5

It’s better to take terumah from a whole small onion than from half of a large onion. Rabbi Yehuda disagrees and says that it’s better to take terumah from half of a large onion than from a whole small onion. Rabbi Yehuda also said that one may take terumah from onions of cities for those of villages but not vice versa because the onions of cities are of a higher quality.