intervene¹ - v. to come between; to come between in order to settle or solve

invade² - v. to enter an area or country by force with an army

invent - v. to plan and make something never made before; to create a new thing or way of doing something

invest³ - v. to give money to a business or organization with the hope of making more money

investigate - v. to study or examine all information about an event, situation or charge; to search for the truth

invite - v. to ask someone to take part in or join an event, organization or gathering⁴

involve - v. to take part in; to become a part of; to include

iron - n. a strong, hard metal used to make machines and tools

island - n. a land area with water all around it

issue - n. an important problem or subject that people are discussing or arguing about

it - pro⁵. a thing, place, event or idea that is being spoken about ("The sky is blue, but it also has a few white clouds.")