1♣ is the lowest bid in bridge, therefore, it is always an opening.
As an opening Edit
- In five-card major systems, a 1♣ opening typically shows four clubs, but may be as few as three. Typically with 3-3 in the minors, one opens 1♣.
- In four-card major systems, a 1♣ opening promises four clubs.
- In strong club systems, 1♣ is the strong, artificial and forcing opening, promises usually 16+ HCPs but nothing about the shape.
- In strong diamond systems, 1♣ is the catch-all opening used when there are opening values and no other opening bid is appropriate. It may be as few as two clubs.