に
1. at (place, time), in, on, during
2. to (direction, state), toward, into
3. for (purpose)
4. because of (reason), for, with
5. by, from
6. as (i.e. in the role of)
7. per, in, for, a (e.g. "once a month")
8. and, in addition to
9. if, although
tbd
ずつ， づつ
1. apiece, each
2. at a time, piecemeal
各(一个)，每一(种)，每一个；一次一点地；逐个地、逐步地