+118725 
+118725 I didn't know that you spelt caret like that! I learn some thing every day!
This is an exerpt from Wolfram|alpha,
It seems the shape is a caret, but the symbol is a hat.
Just a technicality, I know - I am sure either is fine.
The hat is a caret-shaped symbol commonly placed on top of variables to give them special meaning. The symbol 
is voiced "
-hat" (or sometimes as "
-roof") in mathematics, but is more commonly known as the circumflex in linguistics (Bringhurst 1997, p. 274).
Uses of the hat in mathematics include:
1. To denote a unit vector (e.g., 
) or an estimator (e.g., 
).
2. To denote an estimator, e.g., 
for the sample mean.
3. As the growth rate of 
in hat calculus, e.g., 
(Jones 1965, who however used the symbol 
instead of a hat).
