User

Of everyone registered in the system, some may have an access account and be able to authenticate in the system (see figure below). Those who have an access account are system users. Thus, every user is a person, although the reverse is not necessarily true, since there may be people without access accounts who cannot sign in to the system.

Note that a user might have their account temporarily blocked in the system and may not be able to sign in, yet will still remain a user. Thus, some people are system users and, out of all the users registered in the system, some may have blocked accounts.