Small-> Smaller (Short Adj+Er)

Slow-> Slower (Short Adj+Er)

Fast-> Faster (Short Adj+Er)

Thin-> Thinner (Short Adj+consonant n +Er)

Thick-> Thicker (Short Adj+Er)

Pretty-> Prettier (2 syllables Adj ended with thay y thành i +er)

Ugly-> Uglier (2 syllables Adj ended with y bỏ y +ier)

Long-> Longer (Short Adj+Er)

Short-> Shorter (Short Adj+Er)

Heavy-> Heavier  (2 syllables Adj ended with y bỏ y +ier)

Light-> Lighter (Short Adj+Er)

Tall-> Taller (Short Adj+Er)

big-bigger

slow-slower

fast-faster

thin-thinner

thick-thicker

pretty-prettier

ugly-uglier

long-longer

short-shorter

heavy-heavier

light-lighter

tail-tailer