A superlative is a grammatical form used to express the highest degree of a quality among three or more items, often formed by adding the suffix "-est" to an adjective or using the word "most" before it. For example, "tallest" is the superlative form of "tall," and "most beautiful" is the superlative of "beautiful." Superlatives are commonly used in comparisons to highlight the extreme nature of a characteristic, such as in phrases like "the best" or "the fastest."