Knowing when to use a specific suffix in a word requires understanding the rules and patterns of word formation in English.  Identify the Part of Speech: Determine the part of speech you want the word to be (noun, verb, adjective, etc.). Understand the Meaning: Consider the meaning you want to convey.  Analyse the Root Word: Start with a base word you wish to modify or extend. Observe Common Patterns: Pay attention to common suffix patterns used with certain types of words.  Read and Listen: Read extensively and listen to fluent speakers.