残業って英語でなんて言うの？

The time that you work over your working hours is called "Overtime."
I did ten hours of overtime this week.

You can also explain this time as "extra hours."
I worked some extra hours this month.

We say overtime because it is working over our normal hours.
"I have signed up for overtime this weekend".
We also say when we are exhausted and have worked too much, 'I am overworked'.
It is similar in meaning we are working more than we are required to.

Overtime is the most commonly used expression. But you could also say extra time.

If you work additional hours, either at the end of your usual working day or as extra hours, for example on a Saturday or Sunday, this is known as 'overtime.' In the UK, overtime is not usually a voluntary activity and workers would expect to be paid for their time. however, if they do work voluntarily or without payment, it may be called: 'unpaid overtime.'

"Overtime..".is the most commonly used phrase... to accurately describe the situation
where are contracted to have a 35 hour week...and then do 6 more hours to help
the company make a deadline...or finish an order...This is OVERTIME;-D

"overtime (OT)" is when we work beyond the amount of hours we are supposed to in a week/month.
"I work a lot of overtime in my office because I just have too much work and not enough time to do it."

Overtime is defined as the time you work, over your set and agreed hours in employment. Sometimes overtime is paid at a higher rate than your regular hours.