こちらがあなたの鍵だ。

this way (direction close to the speaker or towards the speaker); this direction; here (place close to the speaker or where the speaker is); this one (something physically close to the speaker); I; me; we; us; this person (someone physically close to the speaker and of equal or higher status)

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

you (referring to someone of equal or lower status); dear (what a wife calls a husband)

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

key; lock

be; is; indicates past or completed action; indicates light imperative