Identify prefixes and suffixes of words by first noting the root word that they are attached to. The affixes are generally not complete words on their own, unlike the root words, which can always stand alone. For example, the word "preheating" contains a root word, "heat," as well as the "pre-" prefix and the "-ing" suffix.
Prefixes and suffixes are two of the 11 forms of affixes, or parts of speech that attach to root words. A prefix attaches before the stem, as the root word is called linguistically, while an suffix appears after the stem. By attaching these affixes, the meaning of the stem changes to create a new word. For example, the meaning of the word "do," to perform or accomplish, is reversed when you attach the prefix "un-," Likewise, the suffix "-er," when attached to the stem "work," which means exertion or employment, specifically describes a person who exerts or is employed. This latter suffix is an example of an agentive suffix.
Other commonly used affixes in the English language include circumfixes and simulfixes. The first affix surrounds the stem with two related parts, as with the beginning and terminating "en" affixes in the term "enlighten." A simulfix switches letters within the word, typically in order to pluralize according to irregular rules. The relation between foot and feet, or mouse and mice, are examples of simulfixes.