Ex
In short
Ex is a prefix used to indicate that something was previously true or that a person has left a specific role or relationship.
In plain words
It means something is in the past. You use it to show that a status has changed from what it used to be.
A simple example
If someone was a manager but is no longer in that job, they are called an ex-manager. A person who is no longer married to their partner is an ex-spouse.
Why it matters
It helps people quickly understand the current status of a person or thing. It provides clarity about history versus the present moment.
Easy to mix up
Do not confuse it with the letter X used as a symbol for a mistake or a mark.