A development of national significance (DNS) is a planning application for a large infrastructure project of national importance; for example, a wind farm, power station or reservoir.
Cais cynllunio am brosiect seilwaith mawr o bwys cenedlaethol yw datblygiad o arwyddocâd cenedlaethol (DAC); er enghraifft, fferm wynt, pwerdy neu gronfa ddŵr.