"Tablespoon" may be abbreviated as T (note: uppercase letter), tbl, tbs or tbsp.
A typical large dinner spoon is about 1 tablespoon in size. It is not often the case, but some might consider the dinner spoon as the one used towards a normal bowl of soup or cereal. At any rate, it is not to be confused with a regular spoon for the amount of 1 tablespoon is a bit larger than a regular one.
The seldom-used imperial (post-1824 British) tablespoon is defined to be 18 mL, which is 20% larger than the Queen Anne tablespoon used in the USA. Thus, the Queen Anne (USA) tablespoon is 5/6 the size of the British one. The Australian (metric) tablespoon is even bigger, at 20 mL, while the teaspoon remains at 5 mL to give 4 teaspoons per tablespoon instead of the 3 teaspoons used elsewhere.