In order to answer this question, you first need to understand what a root word is. A root word is the most basic part of a word which has a meaning on its own and which is used to add prefixes and suffixes to in order to create new words. In the case of the word <em>visibility, </em>the root word is vis. It comes from Latin verb videre, which means to see. So if you add suffixes to vis, you will create a new word. For example, if you add -ibility to it, you will create the word visibility.
