The board foot is a unit of volume derived from the imperial system of units with the symbol FBM.
1 board foot is equal to the volume of an object one foot in length, one foot wide and one inch thick. It is therefore equal to 1/12 ft³.
The board foot is the unit used to measure rough or planed lumber. For example 2 x 4 timber when planed actually only measures 1.5 in x 3.5 in. This takes into account the wastage when planing. The board feet measurement in this case would represent the wholesale amount. Where the loss in board feet (and planing) only applies to width and thickness, the actual length is used - as there is no loss when cutting lengths.
The tablespoon is a unit of volume in the US customary system and uses the symbol Tbsp.
In the kitchen, the tablespoon is the larger of the commonly used spoons served at the table and represents 1/2 US fluid ounce or, expressed in SI / metric format; 14.78676 ml.
This is often expressed as equivalent to 3 teaspoons (3 Tsp) although strictly speaking it is a little under the size of 3 metric teaspoons (5 ml) at 4.92892159375 ml. It was established to assist normal kitchens with recipes without the need for specific measuring equipment or devices. Although many spoons differ in sizes (and very rarely is a spoon filled accurately) it allowed for a decent "catch-all" and gave a "good enough" result most of the time.