Thank you is an important word, but it’s too bad it is often misused. There is thank you and thank-you. However, these two forms have three different uses:
Thank you = verb form
Thank-you = noun
Thank-you = adjective
Thank you is from the verb “to thank.” The object is “you.” You can tell if thank you is the right word, if you put the pronoun “I” in front, which is the true meaning. (This meaning is shortened today to the familiar thank you. It is always two words.)
Thank you for attending the meeting. (I thank you for attending the meeting.)
Thank you for answering my questions. (I thank you for answering my questions.)
Thank-you is a noun. An article, such as a or the, will precede it.
I want to give you a big thank-you for your invitation.
The conference is nearly over. It is time for the thank-yous.
Thank-you can also be used as an adjective. A noun will follow.
I must send him a thank-you note.
The thank-you speech went on forever.
Thank you for reading this BizWritingTip on the rationale for using the thank-you.