(1) A task that someone is given to do, especially a military task. (2) A task that someone considers an important duty.

Your own *mission* in life can be anything you pursue with almost religious enthusiasm. People with a mission—whether it's stopping drunk driving, keeping the town's public areas clean, increasing local recycling, or building a community center—very often succeed in really changing things.

A person undertaking a mission, and especially a religious missionary.

Beginning around 1540, an order of Catholic priests known as the Jesuits began to send its members to many parts of the world to convert peoples who believed in other gods to Christianity. Wherever they went, the Catholic missionaries built central buildings for their religious work, and the buildings themselves became known as *missions*; many 17th-century missions in the American West and Southwest are now preserved as museums. Their foes, the Protestants, soon began sending out their own missionaries, and today Protestant missionaries are probably far more numerous.

Someone sent out to represent another; an agent.

Like *missionaries,* emissaries are sent on missions. However, emissaries are more likely to be representing governments, political leaders, and nonreligious institutions, and an emissary's mission is usually to negotiate or to gather information. So a president may send a trusted emissary to a war- torn region to discuss peace terms. A company's CEO may send an emissary to check out another company that they may be thinking of buying. And a politician may send out an emissary to persuade a wealthy individual to become a supporter.

(1) The act or process of sending something from one point to another, especially sending electrical signals to a radio, television, computer, etc. (2) The gears by which the power is passed from the engine to the axle in a motor vehicle.

Since *trans-* means “across” (see TRANS), it's not hard to see the meaning of *transmission*. Disease transmission occurs when an infection passes from one living thing to another. TV signal transmission can be interrupted by tree leaves, including moving leaves and branches during a storm. Your car's transmission *transmits* the engine's power to the axle, changing the gears to keep the engine working with maximum efficiency at various speeds.

(1) To force (someone) to do something. (2) To make (something) happen.

The prefix *com-* acts as a strengthener in this word; thus, to compel is to drive powerfully, or force. So you may feel compelled to speak to a friend about his drinking, or compelled to reveal a secret in order to prevent something from happening. A *compulsion* is usually a powerful inner urge; a *compulsive* shopper or a compulsive gambler usually can't hold onto money for long. You might not want to do something unless there's a *compelling* reason; however, a compelling film is simply one that seems serious and important.

(1) To drive or force out. (2) To force to leave, usually by official action.

To expel is to drive out, and its usual noun is *expulsion. Expel* is similar to *eject,* but *expel* suggests pushing out while *eject* suggests throwing out. Also, ejecting may only be temporary: the player ejected from a game may be back tomorrow, but the student expelled from school is probably out forever.

To urge or drive forward by strong moral force.

*Impel* is very similar in meaning to *compel,* and often a perfect synonym, though it tends to suggest even more strongly an inner drive to do something and a greater urgency to act, especially for moral reasons. But when *impel* takes its noun and adjective forms, it changes slightly. So an *impulse*—such as “impulse buying,” when you suddenly see something cool and know you've got to have it—often isn't based on anything very serious. And *impulsive* behavior in general, such as blurting out something stupid on the spur of the moment, is the kind of thing you're supposed to get over when you grow up.

(1) To keep (something) out or away. (2) To drive back.

Since *re-* can mean not just “again” but also “back” (see RE-), *repel* means “drive back.” *Repel* has two common adjective forms; thus, a *repellent* or *repulsive* odor may drive us into the other room. Its main noun form is *repulsion.* Magnets exhibit both attraction and repulsion, and the goal of an armed defense is the repulsion of an enemy; but we generally use *repulsion* to mean “strong dislike.” In recent years, *repulse* has been increasingly used as a synonym for *repel* (“That guy repulses me”).