Is “thankyou” acceptable as a single word?

Question

I was doing a small piece of language translation in Google Translate, and it detected the use of "thankyou" in the text and asked "do you mean - thank you".

Is the single word version - thankyou - an aberration?

Answer 1

Thank you is a sentence. If you want to use one word, thanks is acceptable. However, thankyou is not acceptable as a single word.

Answer 2

Thankyou is not a word; hence unacceptable. Also it looks illiterate, because literate people know how to spell "thank you".

Answer 3

No, thankyou is not an aberration. It just has a different definition.

• thank you (verb to thank, direct object you) — this is how you say thank you. Essentially short for "I thank you".
• thank-you or thankyou (noun) — an act of thanking. As in: "He gave a big thankyou for..."; "There were thank-yous all around".
• thank-you or thankyou (modifier before a noun) — as in "a thankyou card".

For the noun and modifier forms, most dictionaries seem to prefer the hyphenated thank-you, but also list thankyou as a valid alternative form.

Sources: Wiktionary, Dictionary.com.

But Merriam-Webster only lists the hyphenated form, not the single-word form.