Tune is a melody or song, especially one that's simple enough to remember and hum along to. When you hear a catchy tune on the radio, you might find yourself whistling it hours later. Folk songs, national anthems, and nursery rhymes are all tunes that stick in people's heads.

The word can also mean to adjust something until it works perfectly. Musicians tune their instruments before playing, carefully adjusting strings or valves until each note sounds exactly right. You can tune a radio to find the clearest signal for your favorite station. Mechanics tune up car engines, adjusting dozens of parts so everything runs smoothly together.

When people are in tune with each other, they understand and agree with one another naturally. Best friends are often in tune about what they find funny or interesting. The opposite is being out of tune, which describes both musical notes that clash unpleasantly and people who don't understand each other well.

You might also hear expressions like change your tune, which means to change your opinion or attitude suddenly, or to the tune of, meaning a total amount, as in “The school fundraiser raised money to the tune of five thousand dollars.”