hyphens - Should I hyphenate "Thank You"

When writing in English I am often told that Thank-You is incorrect.

Contradictory to this many dictionaries have it hyphenated, such as:

My question is which is the correct way?

Thank You

Answer

Ah, I presume you mean you looked up thank-you, which is an existing noun but not the same thing at all as the common idiom thank you.

Merriam-Webster tells us:

Full Definition of THANK-YOU

: a polite expression of one's gratitude

Origin of THANK-YOU

from the phrase thank you used in expressing gratitude

First Known Use: 1792

Now, the phrase “thank you” is indeed always written without a hyphen.

But when we transform phrases into nouns, we use (often) hyphens to indicate that those words belong together as a set phrase, and together they become a noun:

After the wedding they sent thank-yous to the guests.

As with many nouns, we can use thank-you attributively ("as an adjective") to modify another noun:

I sent her a thank-you note.