Unbreakable means impossible or extremely difficult to break, damage, or destroy. Some things are unbreakable in a physical sense: a diamond is nearly unbreakable because of its molecular structure, and modern smartphone screens use special glass designed to be unbreakable (though they don't always live up to that promise!). Museums display valuable artifacts behind unbreakable glass to protect them from accidents or theft.

The word also describes bonds, promises, or spirits that won't break under pressure. A friendship might seem unbreakable when it survives disagreements, distance, or difficult times. An athlete recovering from injury might show an unbreakable spirit, refusing to give up despite setbacks. A code might be called unbreakable if experts believe no one can crack it.

When something proves unbreakable, it demonstrates remarkable strength or resilience. The opposite would be fragile or breakable. Notice that unbreakable doesn't always mean literally indestructible: sometimes it means strong enough to withstand whatever challenges come its way. An unbreakable promise isn't protected by magic; it's kept by someone determined to keep their word.