By size mostly. That depends on what type of terrapin you are referring to, of course.
You can tell by the rings on his/her shell. Count them and you will get the age.( this doesn't work all the time. Some rings would be broken. My turtle age is somewhere between 13-23 years old)
Rings
I don't know tell me I'm begging you!
if a terrapin is 9 months old how can you tell if its a boy or girl
boy terrapin has spots and woman terrapin smell betterAnd The Guy Terrapins Have Longer Claws
Turtle or terrapin
Disease, old age, wounds, the usual.
A terrapin
yes
No
It help the terrapin to move its head immediately into its shell when predators are near or when they sense danger.
A terrapin is a form of turtle.
a terrapin comes in many species, but is a small turtle
A diamondback terrapin is an omnivore.