# Frequently asked questions - Math

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## When I enter 3xy the number 3 appears in italics. Why?

Math uses multi-character variable names, which is common practice in many disciplines such as economics. The rule is that each variable name consists of a sequence of letters, numbers and dots (the first character may not be a dot).

Thus, if you enter ** 3xy**, it will be considered as a variable name, and variables are printed in italics. However strange this may seem, a variable name

*can*begin with a digit!

The correct way of entering the expression for "*3 times x times y*" is ** 3 x y** (with spaces between the characters) or better still

**.**

`3 cdot x cdot y`