The Earth's axis

An "axis" is an imaginary line that something turns around. For example, a wheel has an axis which is the middle of the circle.

The Earth's axis is an imaginary line through the middle of the Earth from North to South. The Earth spins around this line.

"Axis" is a technical and mathematical term, so it's most often used with other technical words. Here are some examples:

• In math, you can talk about a horizontal (side to side) axis or a vertical (up and down) axis.
• The action of turning around an axis is called "rotation around an axis". "Rotation" is a more technical word for "turning in a circle".

(something) is tilted

Something that is "tilted" isn't straight up and down. It leans to the side a little bit. Things that can be tilted include:

• someone's head
• a picture frame
• an airplane that's flying in the air

Notice that "tilted" is different from "crooked" or "curved". These words both also mean "not straight", but in different ways:

• "Crooked" means that something bends in different directions at sharp angles, like a tree branch.
• "Curved" usually means that something bends smoothly in different directions, kind of like the letter "S".
• When something is "tilted", it can still be straight, but it's just not pointed directly upwards.