まだ手紙の返事をもらっていない。

as yet; hitherto; only; still; not yet (with negative verb); more; besides; unfinished; incomplete; not yet finished with

letter

indicates possessive; nominalizes verbs and adjectives; substitutes for "ga" in subordinate phrases; (at sentence-end, falling tone) indicates a confident conclusion; (at sentence-end) indicates emotional emphasis; (at sentence-end, rising tone) indicates question

reply; answer; response

indicates direct object of action; indicates subject of causative expression; indicates an area traversed; indicates time (period) over which action takes place; indicates point of departure or separation of action; indicates object of desire, like, hate, etc.

to receive; to take; to accept; to get somebody to do something