According to European standards, there are 3 kinds of spoon which you will find in the kitchen: Table spoon, Tea spoon, and Coffee spoon. Table Spoon can carry 15ml. Tea Spoon can carry 5 ml. Coffee spoon can carry 2-3 ml(I guess).
In my childhood when I used to read cooking guides or watch cooking TV program, I used to notice mention of 2 kinds of spoon – Table spoon and Tea spoon. In my home, I always saw only one kind of spoon that was just spoon. I couldn’t really understand what do they mean by ‘table’ or ‘tea’ spoon.
When I came to Switzerland, I saw 2 kinds of spoon. Bigger one using which you eat or drink soup and a smaller one using which you add sugar in your coffee. I observed that the bigger spoon was bigger than the one we used in India and the coffee spoon was smaller. Well, different cultures different size of spoons fair enough!!
Now! I am in UK. Here I am renting a room in a fully furnished old 1950 house. When I was going through the utensils of the house, I found spoons which are exactly of the size we used to use in India. Wait a sec! British use the same size of spoon as Indians use? I also found the bigger spoons which are the same size of Swiss spoons. Something is going on here!!
The spoon Indians use all the time is tea spoon in British sense. Because, Swiss people don’t drink tea same way as British do so they don’t have tea spoon. Most probably British brought British tea drinking in India and along with tea spoon.
May be, Indians might have thought why to have two different size of spoon so let us pick the one which is smaller and cheap. So, Tea spoon become simply spoon in India.**
**This conclusion is just based on my personal observation. My observation can be wildly wrong.