Final answer:
An affix is a word element that is attached to a root word to change its meaning. The affix could be a prefix, which goes at the beginning, or a suffix, which is at the end.
Step-by-step explanation:
The word element attached to a root word that changes its meaning is called an affix. An affix can be a prefix, which is added to the beginning of a root word, or a suffix, which is added to the end of a root word. Both prefixes and suffixes modify the meaning of the root word to create a new word. For example, the prefix 'un-' can be added to the root word 'happy' to form the new word 'unhappy', which has the opposite meaning of the root word.