Anti-requisite
An anti-requisite is a rule attached to a particular module, which says that you can't take this module in some circumstances.
For example, the course catalogue entry for CS2001 states that CS2101 is an anti-requisite. In this case, the reason for the restriction is that CS2101 is an expanded version of CS2001, including all its content plus additional material. It wouldn't make sense for you to be able to take both modules.
As another example, BL2301 has an anti-requisite of BL2101. In this case, BL2301 is a newer module that evolved from BL2101, in which most of its current content was included.
Because it is aimed at beginners, AR1001 has an anti-requisite stating that you can't take it if you are a native speaker of Arabic, or if you have a school-level qualification in it.
It's worth checking anti-requisites carefully before choosing a module. If it has an anti-requisite that you've already passed, then you won't be able to take it. Or it might be that taking this module means that you won't be able to take the anti-requisite in the future.
