Because given standard English pronunciation, if the comparative and superlative didn't have the double "t", they would be pronounced HOAT-er and HOAT-est, which of course, they aren't.
The comparative version of hot is hotter and the superlative version is hottest.
Dative ; hot Comparative ; hotter Superlative ; hottest
The comparative form of hot is hotter, and the superlative form is hottest.
hotter, hottest
hotter, hottest
Adjective: hot Comparative: hotter Superlative: hottest
The comparative version of hot is hotter and the superlative version is hottest.
The comparative of hot is hotter.The superlative of hot is hottest.
Dative ; hot Comparative ; hotter Superlative ; hottest
The comparative form of hot is hotter, and the superlative form is hottest.
hotter, hottest
hotter, hottest
hotter, hottest
hotter, hottest
Dative; warm Comparative; warmer Superlative ; warmest
The comparative form of hot is "hotter". The superlative form is "hottest".
The base word is hot. Hotter is the comparative form, and hottest is the superlative form.