Definition: A teaspoon (tsp) is a unit of volume, commonly used in cooking and for administering medicine. It is defined as approximately 5 milliliters.

History/origin: The teaspoon likely originated as a practical measure based on the size of actual teaspoons used for eating and serving. Over time, its volume has been standardized for culinary and medicinal purposes.

Current use: The teaspoon is a widely used unit in recipes, particularly in the United States. It's also used for measuring liquid medications, though precise measurements are often recommended using calibrated droppers or syringes.