What Is a Triangle Height?

A triangle's height is the distance from a base to its opposite point

To find a triangle's area, you need to calculate the $\text{base}$$\times \text{height}$. A triangle's base can be any of its sides, so its height is the length of the altitude to that side.

In other words, the "height from a vertex" is the length of the altitude from that vertex to the opposite side. In triangle ABC below, the "height from C to AB" is the length of CD, the altitude from C to AB.

In the image above, the blue lines are the triangles' altitudes. The triangles' heights are equal to the lengths of the altitudes.

Since a triangle can have three different bases (each side can be a base), they can also have three different heights. However, each height only corresponds with one base, and each base corresponds with exactly one height—if you mix them up, your calculations will be messed up!