Five milliliters is 0.17 fluid ounces. A fluid ounce is a unit of measurement used mainly in the United States to measure the volume of fluids or liquids.
There are several different types of ounces, including the metric ounce, international avoirdupois ounce and the international troy ounce, used to measure weight and distance. There have been more throughout history, but these three are the ones in use as of 2015. The avoirdupois ounce is roughly equivalent to 28 grams and is used in the United States as a measure of weight. The troy ounce is used specifically as a measure of weight for gems and precious metals and is roughly equal to 31 grams.