Common Words:
* Impossible: Not possible.
* Impatient: Lacking patience.
* Important: Of great significance.
* Impress: To make a strong impression on.
* Improve: To make better.
* Imprudent: Not wise or cautious.
* Impulsive: Acting suddenly without thinking.
* Immense: Extremely large.
* Immediate: Happening at once.
* Immature: Not fully developed.
* Imitate: To copy or follow as a model.
* Immigrant: A person who comes to live permanently in a foreign country.
* Immobile: Unable to move.
* Immune: Protected from disease.
* Impact: To have a strong effect on.
* Impartial: Fair and unbiased.
* Implicate: To show that someone is involved in a crime.
* Imply: To suggest something without saying it directly.
* Import: To bring goods into a country.
* Impose: To force something on someone.
* Impossible: Not possible.
* Improbable: Unlikely to happen.
* Improper: Not suitable or correct.
* Impulsive: Acting suddenly without thinking.
* Impure: Not pure or clean.
Less Common Words:
* Impeach: To formally accuse a public official of wrongdoing.
* Impediment: Something that hinders or obstructs.
* Imperceptible: So slight as to be almost impossible to notice.
* Imperfect: Not perfect.
* Impersonate: To pretend to be someone else.
* Impertinent: Rude and disrespectful.
* Impetuous: Acting quickly without thinking.
* Implacable: Impossible to appease or satisfy.
* Implausible: Not believable.
* Implement: To put into effect.
* Implicit: Understood though not directly stated.
* Implore: To beg earnestly.
* Imply: To suggest something without saying it directly.
* Impoverished: Made poor.
* Impregnable: Impossible to capture or overcome.
* Impress: To make a strong impression on.
* Impromptu: Done without being planned.
* Improvise: To invent or make something up on the spot.
* Imprudent: Not wise or cautious.
Please note: This is not an exhaustive list. There are many other words that start with the prefix "im".