# The Evaluate Command

The **Evaluate** command is used to do numeric evaluation of expressions. It is used
on expressions that can be evaluated to a single numeric value. It can also act on Boolean
expressions like "True & False" and on certain relationships between types. The keystroke
for the **Evaluate** command is the "*a*" key.

The **Evaluate** command acts on basic mathematical objects like addition, subtraction,
multiplication, division, powers and roots when the terms in these expression are numerical
values. In complicated expressions, not all of the terms have to be numeric for the
**Evaluate** command to work. The command will evaluate any terms in the overall
expression that can be evaluated to a numeric result.

Note that while the **Simplify** command will simplify 2/4 to 1/2, the **Evaluate**
command will reduce it to 0.5. This is implemented this way because we typically would want
1/2(x + 2x + y) to simplify to 1/2(3x + y) not 0.5(3x + y).

On expressions that involves Real numbers the **Simplify** command and the **Evaluate**
command typically produce the same result. So if we have 3.4*7*x, both **Simplify** and
**Evaluate** will produce 23.8*x.