An allied country or person is one that supports and works with another nation or individual. It's like being part of a team.
When we talk about countries being allied, it usually means they have a formal agreement to help each other out, especially during times of conflict or war. For example, the US and UK are often considered allied because they share many values and work together on international issues. Sometimes, two countries will form an alliance to counterbalance a more powerful nation in the area.
It's worth noting that when used as an adjective, "allied" can also mean connected or related in some way. For instance, you might talk about an allied group of people with similar interests or goals.
Joined as allies.
To unite, or form a connection between, as between families by marriage, or between princes and states by treaty, league, or confederacy.
