What is a group of letters added to the beginning of a root word called?

A group of letters added to the beginning of a root word is called a prefix. Prefixes are important because they modify the meaning of the root word to which they are attached. For instance, when you add the prefix "un-" to the root word "happy," it changes the meaning to "not happy." Understanding prefixes helps with vocabulary expansion and comprehension, as it allows readers to deduce the meanings of unfamiliar words based on their roots and the prefixes attached to them.

In contrast, a suffix is added to the end of a root word, while the term affix refers to any addition (including both prefixes and suffixes) used to alter the meaning of a word. A compound word is formed when two or more root words are combined into one new word, which is different from the concept of adding letters to the beginning of a single root word.