In the customary system of measurement, a teaspoon (tsp) is a unit of capacity that is equal to 5 milliliters or 5 ml.
The teaspoon is used to measure the capacity of things that are really small. In the figure above, we show two kitchen utensils.
The one on top is an actual teaspoon or the spoon that is used to drink tea. The capacity of the teaspoon is of course 5 ml.
The one at the bottom is a measuring spoon that is equal to 1 teaspoon or 5 ml as well. This one can be used when cooking or baking.