thinnest
Thinnest is the superlative degree of thin.
thinner
Thinnest
thinner, thinnest
thinner, thinnest
Thinnest is the superlative degree of thin.
Comparative: thinner Superlative: thinnest
The superlative of slim is slimmest.
thinner
Thinnest
thinner, thinnest
thinner, thinnest
thinner, thinnest
thinner, thinnest
thinner, thinnest
There is no procedure (except maybe looking it up in the dictionary, if you don't know on your own). The comparative of thin is thinner; the superlative is thinnest.
Big Small Tiny Tall Fat Thin Smart Stupid Strong Weak Tidy Messy Dirty Clean