The double one in '01

Slang for darts

Scoring 45 points in a throw

The metal portion of the dart (where you grip the dart)

A section of a number

Hitting 3 double bulls in one throw

The double bull

When you have a double 1 left to win the game (usually displayed on the board with an 'X')

Winning a game when your opponent threw first.

The center most part of the board, the area is divided into two sections (the single & double bull)