You may also bid without trumps. A no trump bid takes out any bid of the same number. For example, a "4 no" takes out a "4 low" or a "4 high." As with trumps, the highest bidder gets the kitty and may use it to improve his/her hand.
See Also
Playing the Game
New Game
Dealing
Bidding a Trump
The Kitty
Playing with Trumps
Cutting
Playing a No trump
Reneging
Hints