Inflection

Inflection (or inflexion) is a piece added to a word to express variations in grammar. The added bits are called affixes. They are prefixes (in front), suffixes (at the end) and infixes (in the middle). They are added to the "root", the part of the word which does not change.
Some languages such as Latin or Sanskrit have complex inflections that they apply to most of their words. Others, such as English, are less inflected. Some, such as Mandarin Chinese, use no inflections.
Examples in English: