- John is taller than Peter.
- Alice is cleverer than Mary.
The superlative (e.g. tallest, sharpest, strongest, heaviest, shortest etc.) is used to compare somebody or something with the whole group to which she/he/it belongs.
- John is the tallest boy in the class.
- Alice is the prettiest of the four girls.
- He is the best player in the team.
When a group has only two members, we prefer the comparative to the superlative.
- Incorrect: Take the shortest of the two routes.
- Correct: Take the shorter of the two routes.
- Incorrect: She is the prettiest of the two sisters.
- Correct: She is the prettier of the two sisters.