in-, il-, im-, ir-

The prefix in- changes its form to il- before an l; to im- before b, m or p; and to ir- before r. This prefix (and its variations) have two meanings.

Meaning 1: not, without

• Tom’s inability to whistle always frustrated him.
• The argument was illogical.
• What you are suggesting is impossible.
• Leaving the door unlocked was irresponsible.

Meaning 2: in, into

• The surgeon made an incision in the patient’s abdomen.
• The ancient manuscript was richly illuminated in gold.
• The family immigrated to Canada in 2004.
• Irradiating food prolongs its shelf life.