A more thorough explanation:

actus

Actus means an action or thing that is done. It can also refer to a law that has been passed by both houses of Parliament but not yet approved by the monarch. In Roman law, it refers to a right to drive cattle or a carriage across someone else's land.

• His actus of kindness towards the homeless man was appreciated by many.
• The actus that was passed by the Parliament was awaiting the monarch's approval.
• The farmer had the actus to drive his cattle across his neighbor's land.

The first example shows how actus can refer to a general action or deed. The second example illustrates how actus can refer to a specific type of law. The third example shows how actus can refer to a right to use someone else's land for a specific purpose.