The unique name given to (or chosen by) a user on some Web sites and commercial systems. The User ID and sometimes an accompanying password is used by the service to allow access to the system and/or to track information about you.
A string of letters and/or numbers (e.g., your name) that uniquely identifies you online. Your userID is also the first part of your e-mail address. For your protection, every userID has an associated password.