An ally is someone who supports and stands with another person or group, especially when they face challenges or opposition. In wartime, allied countries fight together against a common enemy. During World War II, the United States, Britain, and the Soviet Union were allies against Nazi Germany. In everyday life, an ally agrees with you and actively helps when you need it.

The word suggests more than casual friendship. When your classmate faces unfair treatment and you speak up for them, you're acting as an ally. When someone joins a cause they believe in, even if it doesn't directly affect them, they're being an ally to that movement. Allies listen, learn, and take action rather than just offering sympathy from the sidelines.

You can ally yourself with a person or cause, which means choosing to support them publicly. Countries form alliances (formal agreements to support each other), and these partnerships can shape history. The strength of being an ally lies in loyalty and courage: standing with others when it costs you something, not just when it's easy or popular.