A potent herbicide and defoliant used by US forces in the Vietnam War.

A substance, such as a surfactant, that reduces the surface tension of a liquid, allowing it to spread across and penetrate the surface of a solid.

Any organism or substance added to a food product (such as dough or batter) that makes it rise when cooked.

(chemistry) Any substance that oxidizes, or receives electrons from, another; in so doing, it becomes reduced.

(chemistry) Any substance that reduces, or donates electrons to, another; in so doing, it becomes oxidized.

A person who finds jobs for actors, models, and other people in the entertainment business.

The substance that creates the buoyancy of a balloon or other airship; normally hydrogen, helium or hot air.

(grammar) A noun that denotes an agent that performs the action denoted by the verb from which the noun is derived, such as "rider" derived from "to ride", or "cutter" derived from "to cut".

(espionage) A spy who pretends to work for one side, when they are actually working for or passing information to the other.

a catalyst