5K

Noun

 * 1)  A road race over 5 000 metres.
 * 2)  A display device or item of content with approximately 5,000 pixels in the horizontal axis.

Usage notes
When written in its expanded-out form, "5000 metres" typically denotes that the race is run on a track, as compared to 5K, which denotes the race is run on a road.