I'm oncall this ...!

What does it mean when someone say “I’m oncall this Monday, can we postpone our gathering?!”

My wife is on call today! She is a doctor and it means that she must be available to go to the hospital immediately if she is called.

“She is on call duty today. As a doctor she has to attend medical emergencies if she is called.”
Is this sentence OK?

‘Call duty’ is not used in combination.
Either:
She is on duty today…
or
She is on call today…

Being ‘on duty’ indicates that she is at the hospital working. Being ‘on call’ indicates that she has to be available to go to the hospital if they contact her.

Beeesneees,
Can I say : ‘She is at call on duty today.’?

no

‘on call’ is a set phrase.

That was really helpful answers! Thank you very much guys :slight_smile: