Argument completion makes it easier to enter Maple commands.  When enabled, as you type commands in 2-D Math or 1-D Math, Maple offers automatic completions for arguments in many useful cases by displaying a popup list of suggested completions.

To use argument completion:

The argument completion list can include examples for some suggested items.  In such a case, if you select that entry, the example is inserted.

This works similarly to how it works in the document.  The only difference is to select an item with the mouse, you must double-click the item.

Argument completion is not enabled by default. You can disable/enable it from the Options Dialog.

By default, Tab is the key you use to accept an entry from the list of available completions. If you want to enable the use of the Enter (Return on Mac) key as another way to accept an entry from the list of available completions, you can do so in the same tab of the Options Dialog.

Argument completion works on some expressions.  These suggestions can appear when you are typing a function call of the form commandname(arguments).  Typically, the popup list would appear in one of these cases:

Maple checks both your current session and Maple's library of known names, so, for example, if you have assigned an expression to the name A and then begin typing a function call for which A is a valid option for the first argument, Maple may suggest A.