A suffix is a letter or group of letters added to the end of a word to change its meaning or grammatical function.
Here are some examples:
* -ing (present participle): walk -> walking
* -ed (past tense): walk -> walked
* -er (comparative): big -> bigger
* -est (superlative): big -> biggest
* -ly (adverb): quick -> quickly
* -ness (noun): happy -> happiness
Let me know if you have any other questions!