From The Free On-line Dictionary of Computing (27 SEP 03) :
assignment
Storing the value of an expression in a
variable. This is commonly written in the form "v = e". In
Algol the assignment operator was ":=" (pronounced
"becomes") to avoid mathematicians qualms about writing
statements like x = x+1.
Assignment is not allowed in functional languages, where an
identifier always has the same value.
See also referential transparency, single assignment,
zero assignment.
(1996-08-19)