When you create a dimension, the program draws it on the current layer, using the current dimension style. Each dimension has a corresponding dimension style, which controls the appearance of the dimension, such as the types of arrowheads, text style, and colors of various components.

You can modify existing dimension styles by changing one of the dimension variable settings and then updating the dimension style to reflect the new settings.

Each dimension you create consists of several parts. A dimension line shows where a dimension begins and ends. When you create an angular dimension, the dimension line is a dimension line arc that subtends the measured angle.

Extension lines, also called projection lines, are lines that extend away from the entity for which you are creating a dimension, so that you can place the dimension line away from the entity. Arrowheads form the termination at each end of the dimension line.

Dimension text contains the measured dimension and can also include prefixes, suffixes, tolerances, and other optional text. As you insert dimensions, you can control the dimension text and specify its position and orientation.

Dimensions can also contain other optional components. A leader is a line leading from a feature of the drawing to an annotation. Leaders begin with an arrowhead, and you can use them to place a dimension away from the dimension line or to add notes. When you create a radial dimension, you can add a center mark, which is a small cross that marks the center of a circle or an arc, or you can add centerlines, which are crossing lines that extend out from the center of a circle or an arc.