Triple Point : Triple point of a pure substance is a very stable state signified by constant pressure and temperature. Due to this, triple point of water in Kelvin’s temperature scale, is taken as the upper fixed point.
When we increase the pressure, melting point of a solid decreases and boiling point of the liquid increases. We may get the co-existence of the three states of matter simultaneously by adjusting pressure and temperature. These values of pressure and temperature signify Triple point.
