A more thorough explanation:

malum

Malum is a Latin word that means something bad or evil.

For example, stealing is considered a malum because it is a bad thing to do. Similarly, lying is also a malum because it is an evil act that can harm others.

mala

The definition of malum is straightforward. It refers to anything that is considered bad or evil. The examples given illustrate this definition by showing how stealing and lying are both actions that are considered bad or evil. These actions can cause harm to others and are therefore considered mala.