What is the grammatical term for a word like thank you and please?

There isn't one specific grammatical term for words like "thank you" and "please". However, they fall under a few categories:

* Phrases: "Thank you" and "please" are fixed phrases because they always appear in that exact order and are used as a single unit.

* Interjections: They can be considered interjections as they express emotion or a sudden feeling.

* Social conventions: These words are primarily social conventions used to express politeness, gratitude, or a request.

* Pragmatic markers: They act as pragmatic markers, indicating the speaker's intention or attitude towards the listener.

While there's no single term, understanding these categories helps explain their function in language.