私あての手紙が届いていますか。

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

letter

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

to reach; to arrive; to get through; to get at; to be attentive; to pay attention; to be delivered; to carry (e.g. sound)

indicates a question (sometimes rhetorical); or; whether or not; some- (e.g. something, someone); indicates doubt, uncertainty, etc.; emphatic prefix; suffix forming adjectives or adverbs; in that way