Average teaspoon size is approximately 5-1/2 to 6-1/4 inches, depending upon the manufacturer and the flatware pattern. A teaspoon's bowl is more or less oval in shape and is designed for stirring tea or other liquids in a relatively smaller hot beverage cup such as a teacup or coffee cup. A teaspoon is smaller than both a tablespoon and a dessert spoon.
In practice, a teaspoon is typically used in informal dining, for not only stirring hot beverages such as tea or coffee, but also for eating ice cream and other desserts, for sipping clear broth soups, and for eating more solid foods such as stews. However, other specialty restaurant spoons are designed for these same purposes, with the teaspoon primarily brought out for use with tea and coffee. Many restaurant flatware collections include teaspoons as part of the standard place settings, although it is not used for more formal occasions.
Note that a restaurant teaspoon is NOT equal to the standard unit of measure called the teaspoon, which is precisely 5 mL, and most flatware sets have a teaspoon that can range in capacity from 2.5 mL to 6 mL. RestaurantSupply.com has teaspoons manufactured from several grades of stainless steel, with varying degrees of shine and corrosion resistance. You may purchase restaurant teaspoons in boxed quantities, although boxes of specific collections will vary in total number of spoons included, depending upon the manufacturer and the teaspoon size and pattern.