Knowing when to use "these" vs "those" in a sentence involves understanding the number and proximity of the nouns or objects you refer to. Here's a breakdown of their usage: "These": "These" refers to multiple things or a group of objects that are closer to you, either physically or conceptually. For example, if you have a bunch of keys in your hand, you would say, "I can't find these keys." Here, "these" emphasises that the keys are in your immediate vicinity. "Those": "Those" refers to multiple things or a group of objects that are farther away from you, either physically or conceptually. For example, if you are pointing to a group of trees in the distance, you might say, "Look at those trees!" Here, "those" emphasises the distance between you and the trees.