I will open a new subject here but IMC does not mean necessarily in the clouds. VMC is 5 km , 1500 ft from clouds vertically and 1000 m horizontally.
If you don't have these minimas you are by default in IMC . So BKN at 6000 and you flying at 5000 out of clouds , is called IMC. 4 km visibility is IMC regardless of in or out clouds.