An example or occurrence of something is also called an instance. When talking about two teachers you did not like, you might say that in both instances you felt you didn't learn as much as you should have.
Most commonly, you'll see this word used in the expression, for instance, meaning "for example." Bright colors, for instance pink, green and blue, make you look young and cheerful. Other times, it will mean an occurrence or case. Several instances of cheating have been reported. You can also use instance when taking abut a step in a process. If you have a question about how your test was graded, go to the teacher in the first instance.