Adjacent means next to or neighboring something, sharing a border or boundary. Your desk at school is adjacent to your neighbor's desk if they're sitting right beside you. Two countries are adjacent if they touch along their borders, like the United States and Canada. In geometry, adjacent angles share a common side and vertex, sitting right next to each other like two slices of pizza meeting at the center.

When something is adjacent, there's no gap or space between it and the thing it's next to. Your bedroom might be adjacent to your sister's room, meaning they share a wall. In a city, adjacent buildings stand side by side along the street.

People sometimes confuse adjacent with nearby or close, but adjacent is more specific. A park might be nearby your house, but unless it shares your property line, it's not adjacent. Adjacent means directly touching or immediately next to. When you're looking at a map and someone asks about adjacent states, they mean the ones that actually share a border.