Correspond means to match up with something or to communicate by writing letters.

When two things correspond, they fit together or align in a meaningful way. In math class, when you plot points on a graph, each x-value corresponds to a specific y-value. On a map, the scale might show that one inch corresponds to ten miles in the real world. When you're reading a book that's been translated from another language, each word in English corresponds to a word in the original language, even if they don't match perfectly.

The word also means exchanging letters with someone over time. Before phones and email existed, people would correspond with distant friends and relatives by writing letters back and forth. Two scientists in different countries might have corresponded for years, sharing their discoveries through the mail. Someone who writes letters regularly is called a correspondent. Today, news reporters are also called correspondents because they send reports back to their news organizations, like someone writing letters home.

The key idea in both meanings is connection: things that correspond are linked together in an organized, meaningful way.