The layout engine will calculate and select a width for the specified element.

In the middle of the parent at the appropriate axis.

For background images, contain the image within the element bounds.

For background images, cover the entire element with the image, stretcing and cropping as necessary.

Font size of the current element.

End of the parent at the appropriate axis.

Represents a calc( ... ) expression

The length is a percentage (0-100) of the parent's length. (typically)

The length is in pixels.

Font size of the root element.

Start of the parent at the appropriate axis.

Similar to CSS 'unset', basically means we don't have a value; should only really be used under certain circumstances (e.g. to handle background sizing properly).

The length is a percentage (0-100) of the viewport's height.

The length is a percentage (0-100) of the viewport's largest side/edge.

The length is a percentage (0-100) of the viewport's smallest side/edge.

The length is a percentage (0-100) of the viewport's width.

Determine whether this unit type is dynamic (ie. should be updated regularly) or whether it's constant