A group of letters that you add to the end of a word to change its meaning.
A suffix can make a word longer and give it a new meaning.
Examples:
The suffix -er makes a word mean a person who does something.
I can add the suffix -ful to the end of 'beauty' to make 'beautiful'.
The suffix -est makes a word mean the most of something.
I don't like words with the suffix -less because they sound sad.
If you add the suffix -ness to 'kind', you get 'kindness'.
The suffix -ly makes a word an adverb, like in 'quickly'.