A marker is a type of pen with a thick tip that writes in bold, bright colors. Markers use ink that soaks into paper (and sometimes through it), making them perfect for posters, signs, and artwork. The most common type is the felt-tip marker, which has a soft, spongy point. You might use thin markers for detailed drawings or thick ones to color large areas quickly.

The word also means something that shows a position or marks a spot. A mile marker on a highway tells drivers how far they've traveled. In a board game, you might use a marker to show where your piece is on the board. Scientists place markers in the ocean to track how currents move. A bookmark is a type of marker that shows where you stopped reading.

Markers can also be things that indicate or signify something important. A historian might call an event a marker of change, like how the invention of the printing press was a marker of a new era in human communication. In this sense, a marker helps us recognize when something significant has happened or changed.