> If you say "one bar of butter", "one stick of butter", and "one pat of butter", these can all refer to three different things or the same thing, depending on where you are located. East Coast and West Coast US butter are sold in different size blocks (though both are "8 tbsp") however sometimes you'll find 4tbsp sticks on the west coast that look like 1/2 an East Coast stick that I've heard called pats.

Wat. Never in my life have I seen butter in the (mostly western) US sold in anything other than 1/4 lb sticks. There are long, skinny sticks and short, fat sticks, but they're always 1/4 lb. If you say a "pat" of butter, you're getting roughly a 1/2 Tbsp of butter from me. Definitely not half a stick!