“Do you know if it's mandatory?”
There's a meeting scheduled for this afternoon. You're busy with other work and don't really want to go. You're not sure whether attendance is required at this meeting. When a coworker asks if you're going, you ask this.
Do you know if it's mandatory?
In casual spoken English, people often ask, "Do you know if ___?" to find out the answer to a "Yes" or "No" question. For example:
Do you know if you're having a boy or girl?
Do you know if he's awake?
Answers to "Do you know if...?" can include:
Yes, it is.
Yeah, he is.
No, they're not.
No, I don't think so.
I'm not sure.
No, I don't know.
In formal English for writing and for situations where you don't know people well, you usually use "whether" instead of "if":
Do they know whether the child is a boy or a girl?
When you say that something "is mandatory", it means that you have to do it. Examples of things that are "mandatory" include:
- a mandatory meeting
- mandatory reading (books you have to read for a class)
- mandatory retirement (making people retire when they reach a certain age)
- mandatory military service (men in some countries have to serve in the military for a few years)