Interval quality is a measure of the number of half steps in an interval of a particular size. It can be perfect, major, minor, diminished or augmented. Every interval can be defined by just its size and its quality. An interval's size is the distance between its two notes on a staff, that is, the total number of lines and spaces between two, and is described, for example, as third, fourth, fifth, etc. A third has a size of three staff positions and is major if it has four half steps, minor if it has three half steps, diminished if it has two half steps, and augmented if it has five half steps.