The description of the grease spell states:
A creature that enters the area or ends its turn there must also succeed on a Dexterity saving throw or fall prone.
What about a creature that enters the area and ends its turn there? That is, if a creature enters the area and succeeds at its save (or fails, falls down, and uses its remaining movement to stand up again), then remains in the greased area, does it have to make another save at the end of its turn?