The rule for comparison of adjectives is: -are for comparative and -ast for superlative.

ful, fulare, fulast (ugly, uglier, ugliest)

rolig, roligare, roligast (funny, funnier, funniest)

röd, rödare, rödast (red, more red, most red)

Many adjectives are on the form: [noun]ig or [noun]sk or [noun]isk. This is akin to English [noun]y or [noun]ic or [noun]ish [noun]ean. The -g is silent in everyday speech, thus: "Ja blir toki, nä tokiast!" (I'm going crazy, no craziest!). As in English, long words are often compared by means of mer (more) and mest (most).

For example: Snabb (fast), snabbare (faster), snabbast (fastest); tokig (crazy), tokigare (crazier), tokigast (craziest); excentrisk (eccentric), mer excentrisk, mest excentrisk.

A famous Swedish tongue-twisters is the neuter adjective or adverb västkustskt[1].

The adjectives are affected by the nouns they describe, both depending on singular/plural and gender. For example:

ful (ugly)
ful [singular uter noun] (en ful get -- an ugly goat)
fult [singular neuter noun] (ett fult får -- an ugly sheep)
fula [plural noun] (några fula getter och fula får -- some ugly goats and ugly sheep)

rolig (funny)
rolig [singular uter noun] (en rolig lek -- a fun[ny] (children's) play)
roligt [singular neuter noun] (ett roligt spel -- a fun[ny] game)
roliga [plural noun] (många roliga spel och lekar -- many funny games and plays)

röd (red)
röd [singular uter noun] (en röd stuga -- a red cabin)
rött [singular neuter noun] (ett rött hus -- a red house)
röda [plural noun] (en massa röda hus och stugor -- a lot of red houses and cabins)

Adverbs(usually ending in -ly in English) are formed by using the singular neuter form of the adjective. Example: Tåget går väldigt långsamt (the train is going very slowly).

Some irregular (oregelbundna) Swedish adjectives:

  • Liten or små, mindre, minst. (Little or small)
  • Stor, större, störst. (Big or large)
  • Långsam, långsammare, långsammast. (Slow)
  • Dålig, sämre, sämst. (Bad)
  • Gammal, äldre, äldst. (Old)