The law of similarity is a rule in psychology that says that objects that are similar to each other will tend to be grouped together. If two ideas are similar, people will tend to think of them together.

For example, when people are looking for a specific item in a store, they will often look in the section where items that are similar to the item they are looking for are located. The law of similarity is also used in advertising – advertisers often use images that are similar to the product they are trying to sell in order to make people think of the product.