Sentence examples for sitting in from inspiring English sources

The phrase "sitting in" is correct and usable in written English.
It is typically used to describe someone being present or participating in a particular event or activity. You can use it when you want to specify that someone is actively involved in something, rather than just being present. Example: "I was sitting in on a meeting with the company's top executives." In this sentence, the speaker is emphasizing that they were actively participating in the meeting, rather than just being present.