Prefixes

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What are prefixes?

A prefix is a word part placed in front of a root word that makes a new word or changes a word’s meaning. Prefixes are not words themselves, but they help to form longer words. They always come at the beginning of words and have one distinct meaning.

Most common prefixes

Several prefixes are derived from Latin and Greek roots, which help determine the meaning of words.

  1. dis- means not. Examples: disagree, disconnect, dismiss
  2. in-, im-, il- and ir- mean not. Examples: illegal, impossible, injustice
  3. pre- means before. Examples: predispose, preview
  4. re- means back or again. Examples: return, revise
  5. un- means not. Examples: uncooked, unfriendly

Consider the following examples:

Example 1: Kate saw a preview of the movie.

“Pre” is the prefix meaning before, and “view” is the root word meaning “see.” Therefore, “preview” basically means “see before.”

Example 2: Chris suffered injustice when he was convicted for a crime he did not commit.

“In” is the prefix meaning not, and “just” is the root word meaning “fairness.” Therefore, “injustice” basically means “not fair.”

Prefixes that show direction or position

  1. circum- and peri- (prefixes) mean around (definition)
  2. co-, col-, com-, con-, cor-, sym- and syn- mean with
  3. ec-, er- and ex- mean out of
  4. em-, en-, im- and in- mean into
  5. infra-, hypo- and sub- means below, under
  6. pre- and pro- mean in front of
  7. super- means above or over
  8. trans- means across or over

Consider the following example:

Example 3: The police searched the circumference of the park. (“Circum” means “around,” and circumference is defined as the outer boundary.)

Prefixes that show time

  1. ant-, fore-, pre- and pro- (prefixes) mean before (definition)
  2. post- means after
  3. re- means again

Consider the following example:

Example 4: The clinic specializes in cases of post-traumatic stress disorder. (“Post” means “after,” and “trauma” means pertaining to wounds.)

Prefixes that show quantity

  1. hemi- and semi- (prefixes) mean half (definition)
  2. uni-, mon- and mono- mean one
  3. bi- and di- mean two
  4. cent-, centi- and hecto- mean hundred
  5. kilo- and mili- mean thousand

Consider the following example:

Example: Skylar attended the centennial parade. (“Cent” means hundred, and “ennial” pertains to a period of years.

Prefixes that show negation

  1. a-, il-, im-, in-, ir- and un- mean no, not or without
  2. ant-, anti-, contra- and non- mean absence of, against, not or opposing
  3. counter- means complement to or opposite to
  4. de- means do the opposite of, reduce or remove
  5. dis- means deprive of or do the opposite of
  6. mis- means bad or wrongly

Consider the following example:

Example: Do not disturb Barb while she is working. (“Dis” means “deprive of,” and “turb” means to confuse.)

Combining prefixes and root words

Do not add or omit a letter when you attach a prefix.

Consider the following examples:

Example 1: dis + satisfied = dissatisfied

Example 2: mis + spell = misspell

Example 3: un + acceptable = unacceptable

Prefixes with no hyphen

Most prefixes are added to root words without a hyphen.

Consider the following examples:

Example 1: copayment

Example 2: semiconscious

Prefixes and proper nouns

When there is a prefix before a proper noun, use a hyphen.

Consider the following examples:

Example 1: un-American

Example 2: non-English

Prefixes ending in “a” and “i”

Hyphenate prefixes that end in “a” or “i” when the root words begins with the same letter.

Consider the following examples:

Example 1: semi-invalid (The prefix “semi” ends with “i,” and the root word “invalid” begins with “i.” Therefore, the prefix is hyphenated.)

Example 2: ultra-ambitious (The prefix “ultra” ends with “a,” and the root word “ambitious” begins with “a.” Therefore, the prefix is hyphenated.)

Prefixes and root words with different vowel endings

Prefixes are attached without a hyphen when a prefix ends with one vowel and the root word begins with a different vowel.

Consider the following examples:

Example 1: antiaircraft

Example 2: proactive

Prefixes ending in “e” and “o”

When there is a prefix that ends with “e” or “o” and a root word that begins with “e” or “o,” you can combine them to form one word.

Consider the following examples:

Example 1: coordinate

Example 2: preemployment

Note: There are two exceptions to this rule. They are: “de-emphasize” and “co-owner.”

The prefixes all-, ex- and self-

Hyphenate all words with the prefix “all,” “ex” and “self.”

Consider the following examples:

Example 1: all-inclusive

Example 2: ex-wife

Example 3: self-addressed

When to use a hyphen with the prefix re-

The prefix “re” uses a hyphen when “re” means “again,” and it would cause confusion with another word.

Consider the following examples:

Example 1: Can Doug recover from his illness? (In this case, “re” does not mean “again” and a hyphen is not used.)

Example 2: Patricia must re-press the pants. (In this case, “re” means “again,” and you use a hyphen.)

Example 3: She re-covered the couch twice. (In this case, “re” means “again,” and you use a hyphen.)

When to use a hyphen with the prefix cross-

In some, but not all cases, the prefix “cross” uses a hyphen.

Consider the following examples:

Example 1: Cross-reference, cross-section

Example 2: Crossword, crossroad

“Ante” or “anti”

Use the prefix “ante” if the word means “before or ahead,” and use “anti” if the word means “against or opposite.” In either case, a hyphen is not usually used.

Consider the following examples:

Example 1: The psychiatrist recommended an antidepressant. (In this case, “anti” means “opposite,” and no hyphen is used.)

Example 2: The doctor prescribed an anti-inflammatory to ease the swelling. (In this case, “anti” means “opposite.” Considering the previous rule to hyphenate prefixes that end in “a” or “i” when the root words begins with the same letter, anti-inflammatory is hyphenated.)

What to do when you are unsure

When you are unsure how to use a prefix properly to spell a word correctly, look up the word in a dictionary. Normally, if a hyphen is required, the word has it in the dictionary spelling.