A tweet on mastodon is called a “Post”.
Before Nov 14, 2022 they were called Toots. This was fun but mostly was due to a misunder standing of the english meaning.
this is in responce to this youtube video that arguest that all text posts on social networks should be called tweets which to me makes no sense. The idea that a post on twitter with an image and a image on instagram with text should have a different name because of some fundimental valuye of how it is displayed is wild. The only reason these things ever have different names is for corperate branding purposes.
In a federated world a text post with an image can be displayed differently on different platforms so the way a post is made has no bearing on how it is displayed.