4. Weak - weaker - the weakest
5. Tall - taller - the tallest
6. Short - shorter - the shortest
7. Thin - thinner - the thinnest
8. High - higher - the highest
9. Low - lower - the lowest
10. Heavy - heavier - the heaviest
11. Light - lighter - the lightest
12. Young - younger - the youngest
13. Old - older - the oldest