A suffix is a group of letters attached to the end of a word to form a new word. In English, common suffixes are “-ly,” used to change an adjective into an adverb (“happy” becomes “happily”), or “-ed,” used to express the ast tense of a verb (“like” becomes “liked”). In Italian, suffixes are commonly used at the ends of nouns and adjectives. There is no set of rules that tells you which suffixes can be used. The best way to learn them is to listen for them when native speakers are talking to.