Prefixes and suffixes are sets of letters added to words to form new words. Prefixes are added to the beginning while suffixes are added to the end. Some common prefixes include pre-, inter-, mono-, un-, and re- which mean before, between, one/single, not, and back/again respectively. Suffixes can make words inflectional by changing grammar or derivational by changing meaning. Examples of suffixes include -ment, -ness, -ion, -er, -en, and -able. Rules for adding suffixes include changing y to i before certain suffixes and doubling final consonants. Prefixes and suffixes can be combined to derive new words like prearrangement, intercontinental, and unwilling