How many milligrams does it take to make a teaspoon?

In some countries, the teaspoon is used as a unit of volume, especially in cooking recipes and pharmaceutic prescriptions. It is abbreviated in English as t. or tsp., German and Dutch: TL, from Teelöffel or Theelepel. A teaspoon is often taken to mean 5 millilitres. 1 millilitre of water is 1 gram. Only pure water!