The four letter name vs. Ado-nai

Question

In hundreds of verses (such as Psalms 51:17 אֲ֭דֹ-נָי שְׂפָתַ֣י תִּפְתָּ֑ח וּ֝פִ֗י יַגִּ֥יד תְּהִלָּתֶֽךָ׃) God is named with the word Ado-nai seemingly referring to the same pronunciation and meaning as how we pronounce and use the four letter name Yod Kay Vav Kay.

Why then (especially as the meforshim from the Aramaic on down, when quoting the verse, use H' which symbolizes the name of God) would the text use the word and not the 4 letters? Does the use of the letters A-d-n-y mean something different which would explain its use instead of the 4 letter name which is pronounced the same way?

Answer 1

Throughout Kabbalistic literature you find discussion about how the שם הויה is representative of קודשא בריך הוא, or the זעיר אנפין. The שם אד-ני is representative of the נוקבא דזעיר אנפין, or the מלכות. As such, the names themselves are representative of different aspects of Hashem, as it were.