In Prefix – Definition, Meaning & Synonyms | Learn 30+ Negative Prefixes in English that Help you Understand English Grammar

Prefixes are key building blocks in English vocabulary. They tend to have various meanings, which can be deciphered on the basis of context, common sense, and the process of elimination. Today let’s focus on the prefix “in”, which can mean “in, on, or not”. The prefix in, which has the previously mentioned meanings occurs in several English vocabulary words. Examples include inject, influx, insane, invalid, etc.

Words with Prefix “in” Meaning

Two highly used meanings of ‘in’ are “in” or “on.”Have a look at a few examples:
The prefix, for instance, can mean “in,” such as in the words like inject, to throw “in,” and influx, to flow “in.”

The same prefix ‘in’ can also mean “on,” used in words like Inscribe, which means to write “on,”
Invoke, to call “on.” Hence, the main meanings of in are “in” or “on.”

The prefix ‘in’ can also, however, imply the meaning “not.” This is the trickier aspect of this prefix, but once you familiarise yourself with this, it becomes highly valuable in decoding English vocabulary. Some examples of the meaning “not” include:

  • Independent, which means “not” dependent
  • Insane, which means “not” sane
  • Invalid, which means “not” valid.

Based on the context, or the process of elimination, it becomes easier to determine whether the prefix ‘in’ implies “in, on” or “not.” For example Inject, which has the meaning “throw in,” would have no sense as “not throw.” Similarly, the word insane is of no significance as “on” sane or sane “in;” “not” sane is the best choice.

English Words Prefixed with “in”

Given below is a list of words that contain the prefix ‘in’;

  • Independent
  • Include
  • Involve
  • Invisible
  • Incomplete
  • Indecisive
  • Inculcate
  • Insignificant
  • Inexpensive
  • Insane
  • Inspect
  • Insist
  • Intend
  • Involve
  • Indulge
  • Inbalance
  • Infallible
  • Involuntary
  • Invalid
  • Invariable
  • Insecure
  • Inaccurate
  • Inadmissible
  • Inanimate
  • Incapable
  • Incoherent

Different Spellings of “in”

The prefix “in” has not just three different meanings, but also five different spellings. The change in spelling is dependent upon the stem to which the prefix is affixed. The spelling change is brought about to make the word easier to pronounce. The prefix “in” can exist in the given forms: il, im, in, ir, and ig. Examples of words include
irregular, and ignoble, illegal, imbibe, innate.

Take, for instance, the word “immutable.” The word consists of three morphemes: the prefix in-, the root word “mut,” and the suffix “-able.” The word means “not able to be changed.”
Here you can see that the prefix ‘in’ has changed its spelling to im: that is the prefix has undergone assimilation so that the word is easier to say. The word “immutable” is preferable to “inmutable”. Similarly the word “irresistible,” meaning “not able to be resist,” is a better choice than “inresistible”.

Given below is the five forms of “in” with examples

  • il: Examples include: illegible: “not able to be read”, illegal: “not legal;” illogical: “not logical;” etc.  Here you find that the ‘il’ spelling is preferred to or inlegible, inlegal, inlogical, The change in form happens only when:in’ precedes a stem that begins with the letter “l.”
  • Im: Examples include: immortal: “not mortal”, imbibe: “drink in;” implant: “set in;” etc. ‘in’ changes to im when the root word begins with “m,” “p,” or “b.”
  • In: Examples include: incisor: tooth that “cuts in.”, innocent: means “not guilty;” inculpate: “put the blame on;”
  • Ir: Examples include: irrational: “not rational;” irregular: “not regular.”irrigate: “put a supply of water on;” ‘in’ changes to ir when the root word begins with “r”.
  • Ig: Examples include: ignore: “not pay heed to;” ignoble: “not noble;” and ignominious: “not having a good name.” ‘in’ becomes ig only before a root word that begins with “n.”

Hence the prefix “in” not only has three meanings: “in, on, or not,” but can also be spelt in five different ways: il, im, in, ir, and ig.

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Choosing the Right Prefix!

One of the worst moments you may encounter is when you are not sure which prefix is to be used in a given context. You might often get confused thinking about why is it that the opposite of efficient is inefficient, but the opposite of mature is immature, and the opposite of important is unimportant! The dilemma you face is natural as in English there exist several prefixes that have the same meaning.

One such set of prefixes that imply the same idea is in-, un-, de-, im-, ir-, il-, and non-. All these can all be used as prefixes that mean “not”. Unfortunately, there are no rules that help you to identify which is the right prefix to be used. The use of the appropriate prefix is solely based on common sense and context.

FAQs on In Prefix

1) What are the common meanings of the prefix “in”?
A letter or a group of letters that you keep at the starting of a word is known as a prefix. Prefixes tend to have different meanings which can be identified based on the context. The prefix “in” has the following meanings: “in, on, or not,”

2) What are the five different forms of the prefix”in”?
A letter or a group of letters that you place at the beginning of a word is known as a prefix. The prefix” in” has not just three different meanings, but five different spellings. These are il, I’m, ig, it, and in.

3) Why does a prefix have different forms/ spellings?
The spelling of a prefix changes or alters depending upon the root word to which it is attached. For example, the prefix “in” takes five different forms based on the root word it is attached to. These are il, in, I’m, ig and ir.

4) Give examples for words that have the “im” form of “the In” prefix?

The prefix ‘in’ changes to ‘im’ when the root word begins with “m,” “p,” or “b”. Examples include implant, immortal, etc.


Prefixes being the basics of English grammar requires you to have a proper understanding of them. One of the most common prefixes used in English is “In”. The prefix “in” has three meanings: “in, on, or not,”. It also has five different forms: il, im, in, ir, and ig. Even though comprehending the prefix can be difficult, once you are familiar with it, decoding English vocabulary will be an easy task.

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