Superlative forms are used to describe the highest degree of a quality among three or more items. They often end in "-est" for short adjectives, such as "tallest" or "fastest." For longer adjectives, the word "most" is used, as in "most beautiful" or "most interesting." In English, superlatives help to compare one item against all others in a group. For example, when comparing three cities, you might say New York is the "largest," while Tokyo is the "most populous." This form emphasizes the extreme nature of the quality being described.