The fact that "my lord" doesn't refer to God may be either an accident of usage (a better question is whether "adon" ever refers to God [it does], or do all divine references use the emphatic form? [no, they don't]) or it may be a non-issue because God is the Lord over everything (so not simply "my Lord").

It might also be worth noting the name Adonijah (adoni-yah) means "my Lord is Yahweh").

@JedSchaaf. I have expanded my answer as a response to your comment.

-1 @Alex Balilo asserted, "The term [adoni] has never been used to refer to God in the bible." Have you researched this? Please consider that Adonai is used twice in the Shema, the Jewish prayer that serves as a centerpiece of the morning and evening Jewish prayer services! It's used as a circumlocution for the name of God, YHWH. This falsifies your broad claim.

@Dieter "Adonai is used twice in the Shema" 1. it's not in the text of the Shema so that seems completely irrelevant, it's spoken more than twice, and it's spelled differently from adoni 2. As you'll note אדֹנִי with a chirik is not the same as * אֲדֹנָי* with a kamatz which is the original question is about

@Avi Abraham, so please instruct us. Which one is written and then recited in English correctly? "Hear, O Israel, the L-rd is our G-d, the L-rd is One." OR Hear, O Israel, the lord is our G-d, the lord is One."

@Dieter. Please provide proof that adoni was used to refer to God.

@Dieter Avi and Alex seem to have the mistaken impression that changing an affix to a word makes it a totally different word.

@JedSchaaf yes, it's axiomatic that different words are different. Otherwise why isn't אֲדֹנָי used in the Bible for a human whereas אדֹנִי is used many times for humans?

@Dieter what's the relevance of an English translation here?

Having checked the 161 occurrences of adoni with only that specific masculine singular non-emphatic form with the first-person singular possessive suffix, none of them refer to God. Plenty of other of the hundreds of usages of the stem occur with various affixes that do refer to God, both in normal (adon) and emphatic (adonai) forms.

@Jed Schaaf, Thank you for the additional research regarding the Hebrew! Alex, it was your post, thus the burden of proof rests on you. If you edit your answer to add that proof, I'll happily remove my downvote even if I disagree. Avi, it's relevant because the rabbis started the practice of circumlocution around 2,000 years ago. They substituted a word for YHWH. Check Chabad.org to see whether the Shema written "lord" or Lord" in English and let us know. Also, I understand that this is not a place for argumentation. Please make your best case in your answer. No offense intended.

@AlexBalilo I just said that_adon-i_ doesn't. But that's only saying that "my lord" doesn't refer to God. It says nothing about whether "lord" ever refers to God.

@JedSchaaf and Dieter. If adoni was never used to refer to God, I have no burden to prove. Please cite a verse where adoni is used to refer to God, then I will expand my answer to address that.

@AlexBalilo Because adoni is so specifically narrowed to only "my lord" and none of the other grammatical forms of adon ("the lord," "his lord," her lord," "and the lord," "to the lord," "lord of," "the lord of," "and the lord of," "to his lord," etc.), your claim in your answer is nearly unsubstantiated and not useful for biblical interpretation and hermeneutics.

@JedSchaaf. I will stop commenting until you can provide me a verse where adoni was used to refer to God.

@AlexBalilo I already said it doesn't, but that it's not useful to say that, as well as why I said it's not useful.

@AlexBalilo Using your own specificity, adoni ("my lord") isn't even used in Psalm 110:1; it's l'adoni, which means "to my lord."