Comparative is the grammatical term used when comparing two things.
Superlative is the grammatical term used when comparing three or more things.
For example, looking at melons you can compare their size, determining which is big, which is bigger, and which is biggest. The comparative ending (suffix) common adjectives is generally “-er”; the superlative suffix is generally “-est.” For most longer adjectives, the comparative is made by adding the word “more” (for example, more comfortable) and the superlative is made by adding the word “most” (for example, most comfortable)
If a 1 or 2-syllable adjective ends in “e”, the endings are “-r” and “-st”. Eg: wise, wiser, wisest.
If a 1 or 2-syllable adjective ends in “y”, the endings are “-er” and “-est”, but the y is sometimes changed to an “i”. Eg: happy, happier, happiest.
If a 1-syllable adjective ends in a consonant (with a single vowel preceding it), then the consonant is doubled and the endings “-er” and “-est” are used, for example: big, bigger, biggest.
Some 2-syllable adjectives use the standard “-er” and “-est suffixes”, including adjectives that end in “er”, “le”, or “ow”. For example: narrow, narrower, narrowest.
For most adjectives with two or more syllables, the comparative is formed by adding the word “more,” and you form the superlative by adding the word “most”, for example: colorful, more colorful, most colorful.
Some comparative and superlative adjectives are irregular, including some very common ones such as good/better/best and bad/worse/worst.
Comparative adjectives are used to compare differences between the two objects they modify (larger, smaller, faster and higher). They are used in sentences where two nouns are compared, in this pattern:
Noun (subject) + verb + comparative adjective + than + noun (object).
Eg. Your dog runs faster than Liam’s dog.
In the superlative you talk about one thing only and how it is the best, worst, etc. You do not compare two things.
Eg. She’s the luckiest person I know.