When used as a quantity, such as in a recipe, a teaspoon is the name of several units of measuring volume used primarily in cooking. It is abbreviated as t. or tsp.

1 U.S. customary teaspoon = ¹/₆ U.S. fl. oz (4.93 mL)

1 U.S. customary teaspoon = ¹/₃ U.S. tablespoons

1 Imperial teaspoon = ¹/₈ Imperial fl. oz (3.55 mL)

1 SI teaspoon = 5 mL (used in Australia, Canada, New Zealand and U.K.; also used in the U.S. in pharmacology)

In a more general sense, a teaspoon is any small spoon, usually used to stir the contents of a cup of tea or coffee.

Note that a teaspoon used for stirring hot drinks is unlikely to contain the standard amount of material. For measuring precisely, special measuring spoons are available and should be used.

Other spoon measures include Tablespoon and Dessert spoon. Many recipes call for 'heaping' spoon measures. A 'heaping tablespoon', for example, refers to an inexact volume of the required ingredient, obtained by scooping it up with a tablespoon and not levelling it off.