The maps-to symbol 
specifies the assignment of a value to an argument
by a function. The notation 
is read 
maps to 
(Lang 2002, p. ix).
The ordinary arrow in 
specifies the domain 
and codomain 
. These declarations can be combined, as in 
, 
,
for the function that squares real
numbers. The equality 
gives the value of 
at 
.
The argument need not be a number. If 
is a bilinear
form on a vector space 
over a field 
, then for fixed 
the notation 
specifies a linear
functional (Axler 2024, p. 333).
