Day - Wikipedia. A solar day is the length of time which elapses between the Sun reaching its highest point in the sky two consecutive times. En.wikipedia.org K is the unit symbol for the kelvin, used to measure thermodynamic temperature. En.wikipedia.org A day is approximately the period of time during which the Earth completes one rotation around its axis.
K is the chemical symbol for the element potassium (K is an abbreviation of kalium, the Latin name for potassium).