Cách sử dụng
The expression "not be/feel up to the mark" means that you're not feeling your best or performing as well as you normally do. This can be applied to many situations, such as feeling sick and unable to work, or not feeling confident enough to complete a task. It's a way to express that you're not at your best, and may need some rest or support in order to improve your performance. It's a useful expression to have in your vocabulary, as it can help you communicate your feelings and limitations to others.