In general, function or expression names must be single characters. However,
the system includes a number of predefined functions with names that appear
to be multicharacter—such as gcd, inf, and
lcm—but
that behave like a single character in the sense that they can be deleted
with a single backspace. You can create custom names with similar behavior
that are legitimate function or expression names.
To create a custom name
dtbpF4.0413in2.5841in0ptmathname.wmf
The gray custom name appears on the screen at the insertion point. You can use this name to define a function or expression. You can copy and paste or click and drag this grayed name on the screen, or you can recreate it with the Math Name dialog.