5NT can mean the following:
- After a 1NT or 2NT opening, 5NT is usually an invitation to 7NT, asking opener to bid 6NT if minimum and 7NT is maximum.
- After Blackwood 4NT and a response, 5NT is asking for kings.
- After Gerber 4♣ and 5♣, 5NT shows 3 kings.
- As a voluntary jump bid, 5NT is often Grand slam force.
- After a sequence of control-showing cue-bids, 5NT is often used for trump ask.
5NT is very rarely a signoff and is the least commonly played contract in bridge.