Colloid, in chemistry definition is a heterogenous mixture, of one substance is different from another, when mixed, either of the substance (particularly the solid one), is evenly mixed with each other. It could clearly be seen when one mixes a solution in a suspension state because it forms a cloudy solution, however, in like suspension, it does not settle at the bottom of the mixture. Best example of this is milk. When you mix milk powder to a hot water, the solution is mixed evenly however the color of the water from transparent changes to milkish white.