Relation between phase and line voltage?

For a three-phase, three-wire, system, the line voltage and the phase voltage are numerically equal to each other, and both are measured between any pair of line conductors.

For a three-phase, four-wire, system, the line voltage is 1.732 times the phase voltage. The line voltage is measured between any pair of line conductors, whereas the phase voltage is measured between any line conductor and the neutral conductor.