A suffix is a group of letters added at the end of a word to change its meaning or function. It often alters the word's grammatical category, such as turning a noun into an adjective, modifying tense, or indicating plurality. For instance, the suffix "-ing" can convert the verb "run" into the present participle "running."
The word "suffix" comes from the Latin "suffixus," which is the past participle of "suffigere," meaning "to fasten underneath." This reflects how a suffix is attached to the end of a word.