Turtle, Tortoise, or Terrapin? It all depends on where you live.
In California, a "turtle" is a water turtle. A "tortoise" is
a large land turtle. A "terrapin" is a Diamond Back Terrapin, and
box turtles are called "box turtles."
But leave the sun state, and naming changes. I Britain, a
turtle is a box turtle, and a terrapin is a water turtle.
In Australia...in Canada.
Now, according to the dictionary, all the words mean the same.
So, what is the conclusion? If you write, don't just say you
have "a turtle." I can't tell, whether you have a red-eared
slider or a Galapagos tortoise. Tell me what the species is.
If you don't know the species, describe your animal: how big,
what color, what shapes, spots, stripes, ridges, and so forth.
Here is the beginning of a list:
California: turtle==water turtle, tortoise==landdwelling turtle, terrapin==diamond back