Modifier
Definition: A modifier is a key that can be used in conjunction with a second key and modifies its behaviour. Assistive technology may have its own modifier key so that its keystrokes do not conflict with the keystrokes used by the operating system (e.g. Windows) or other programs.
Category: technology
Credit: RNIB
Source: http://www.rnib.org.uk/livingwithsightloss/computersphones/pages/glossary.aspx