One method of studying prefixes in the English language is to memorize commonly used affixes as well as the meanings each extends to the attached root word, called a stem. Prefixes such as "re-," meaning "again," and "dis-," meaning "reverse," are often used in words such as "replace," "reorganize," "disinformation" and "disingenuous." Also, attach prefixes to common words to practice using them in regular speech.
When prefixes are added to a stem in English, they alter the meaning of the subsequent word but, for the most part, do not change the part of speech from the root word. Thus, the adjective "loyal," when paired with the prefix "dis-," is still an adjective as "disloyal." In contrast, many forms of suffixes, the other major form of affix, change the lexical class.
One major class of English prefixes describes numerals based on three classic languages: Latin, Greek and Sanskrit, although the first two are primarily used in English. Each language uses different prefixes in regard to cardinal or multiple number contexts. The Latin cardinal for two, for example, is the prefix "du-," as in "duplicate," while the number is expressed similarly as the Greek cardinal prefix "dy-," such as with the word "dyad."