To materialize means to suddenly appear or become real and visible, often in an unexpected or almost magical way. When your friend materializes beside you in the hallway, they seem to come out of nowhere. When a deer materializes from the fog at the edge of the woods, it appears as if the mist itself turned into an animal.

When something materializes, it goes from being invisible, imaginary, or merely possible to actually being there in solid form. A plan materializes when it moves from just an idea to actually happening. Your hoped-for snow day materializes when you wake up to find school actually canceled.

Scientists might talk about particles that materialize in experiments. In ghost stories, spirits are said to materialize in old houses (though that's just fiction). When your birthday party finally materializes after weeks of planning, it means all those ideas and preparations have turned into an actual event.

The opposite is dematerialize, when something vanishes or disappears. People also use materialize to mean that something expected or promised finally happens: “Her big career opportunity never materialized” means it didn't end up happening after all. But most often, materialize captures that sense of something suddenly becoming real and present before your eyes.