Degree is a grammatical category which expresses the degree to which some quality is present. English adjectives and adverbs commonly distinguish three degrees: the positive (the basic form), the comparative (expressing a higher degree than is present in something else) and the superlative (expressing a maximal degree).
The comparative is formed with ‘-er’ or with more. The superlative is formed with ‘-est’ or with most. Short words like tall and short tend to prefer –er and –est; longer ones like beautiful and carefully take more and most.
• John is tall (positive).
• Peter is taller (comparative) than John.
• Mike is the tallest (superlative) man I know.
• Ann is beautiful (positive).
• Mary is more beautiful (comparative) than Ann.
• Alice is the most beautiful (superlative) girl in the class.