When to use that or which in a sentence?This is a common question for English language learners. In order to properly use that or which in a sentence, it's important to understand the difference between the two. That is used to refer to a specific item or person, while which is used to refer to a more general item or person. For example, "I saw the dog that was chasing the cat" uses that to refer to a specific dog, while "I saw the dog, which was chasing the cat" uses which to refer to a more general dog. Understanding the proper use of that and which can help improve your English writing and speaking skills.