You’ve probably played with magnets since you were a child. It is likely that you found that magnets attract some materials but not others. You may have found that you can use a magnet to magnetize items like paper clips, nails, and screws. If you played with two magnets you found that they could either attract or repel each other.

Whether you played with metal bar-shaped magnets, rectangular or circular ceramic magnets, you found that the magnet exerted stronger forces at the ends or faces of the magnets. Those regions are called “poles.” If you hang the magnet from a string so it can rotate freely you’ll find the magnet orienting itself north-to-south. The end facing north is called the north pole, the other the south. Like poles repel each other while unlike poles attract, but either end can attract other materials.

Magnetic poles always come in north-south pairs called dipoles (two poles). Some theories predict the existence of isolated north or south poles, called monopoles. But, there have been extensive searches for monopoles over the past decades and none has ever been found.