In Dutch, adjectives change form to show comparison: comparative (groter - bigger) and superlative (grootst - biggest).

1. Comparative (Vergrotende Trap)

• Formation: Generally, add -er to the base adjective.
• groot (big) -> groter (bigger)
• mooi (beautiful) -> mooier (more beautiful)
• snel (fast) -> sneller (faster)
• Spelling Rules:
• Adjectives ending in -r: add -der. (lekker -> lekkerder)
• Adjectives with short vowel + single consonant: double the consonant. (dun -> dunner)
• Adjectives ending in -s: change to -z-. (grijs -> grijzer)
• Adjectives ending in -f: change to -v-. (lief -> liever - also irregular)
• Usage: Used to compare two things/people, often with the word dan (than).
• Mijn huis is groter dan jouw huis. (My house is bigger than your house.)
• Zij rent sneller dan ik. (She runs faster than me/I do.)

2. Superlative (Overtreffende Trap)

• Formation: Generally, add -st or -ste to the base adjective.
• Add -st if the adjective ends in -s or a vowel.
• Add -ste otherwise.
• groot -> grootst (biggest)
• mooi -> mooist (most beautiful)
• snel -> snelst (fastest)
• grijs -> grijsst (grayest)
• duur (expensive) -> duurst (most expensive)
• Spelling Rules:
• Adjectives with short vowel + single consonant: double the consonant before -ste. (dom -> domste)
• Adjectives ending in -s: already ends in s, so just add t. (grijs -> grijsst)
• Usage: Used to indicate the highest degree of a quality among three or more things/people.
• Usually preceded by a definite article (de or het). The ending -e is added to the superlative form when used before a noun or after de/het.
• Dit is het grootste huis. (This is the biggest house.)
• Zij is de snelste loper. (She is the fastest runner.)
• Can be used adverbially with het: Hij rent het snelst. (He runs the fastest.)

3. Irregular Forms Some common adjectives have irregular comparative and superlative forms:

• goed (good) -> beter (better) -> best (best)
• veel (much/many) -> meer (more) -> meest (most)
• weinig (little/few) -> minder (less/fewer) -> minst (least/fewest)
• graag (gladly/like to) -> liever (rather/prefer) -> liefst (most preferably)
• dichtbij (nearby) -> dichterbij (nearer) -> dichtstbij (nearest)

Example:

• Deze appel is lekker, maar die is lekkerder, en die daar is het lekkerst. (This apple is tasty, but that one is tastier, and that one there is the tastiest.)
• Ik drink graag koffie, maar ik drink liever thee. (I like drinking coffee, but I prefer drinking tea.)