Prefix in-

The prefix in- is the derivational bound morpheme mostly attached to adjectives. This prefix does not change the part of speech either. The meaning of this prefix is ‘not’. Look at the examples below:
Prefix Base Derived word Meaning
(Adjective) (Adjective)

in- accurate inaccurate ‘not accurate’
in- tolerant intolerant ‘not tolerant’
in- efficient inefficient ‘not efficient’
in- expensive inexpensive ‘not expensive’
in- fertile infertile ‘not fertile’
in- formal informal ‘not formal’
in- legal illegal ‘not legal’
in- moral immoral ‘not moral’
in- perfect imperfect ‘not perfect’
in- polite impolite ‘not polite’
in- complete incomplete ‘not complete’
in- consistent inconsistent ‘not consistent’
in- regular irregular ‘not regular’
in- responsible irresponsible ‘not responsible’
in- relevant irrelevant ‘not relevant’

From the examples above, the rule of prefix in- attached to adjectives can be stated as: {in-} + ADJECTIVE --> new ADJECTIVE. This rule says that the prefix in- attached to an adjective creates a new adjective. The new adjective is indicated by the change of meaning ‘not’ in the derived word. The prefix in- attached to nouns are very rare. The following are the examples of the prefix in- attached to nouns.

Prefix Base Derived word Meaning
(Noun) (Noun)in- balance imbalance ‘absence of balance’
in- decorum indecorum ‘lack of decorum’
in- decision indecision ‘the state of being unable to decide’