Adding endings to words that end in a double ‘l’

In American English, adding endings such as –ment, –ful, or -ness to words that end in a double ‘l’ poses no spelling problems. You just add the endings to the basic word:

 

install    installment

skill       skillful

small     smallness

 

If you are adding –ly, though, you do need to drop the final ‘l’ before adding the ending:

 

chill       chilly

frill        frilly

 

In British English, the situation is different: words ending in double ‘l’ drop the final ‘l’ when the endings – ment or –ful are added:

 

install    instalment

skill        skilful