What happens if my ball is partly in the general area and partly in a penalty area?
Your ball is treated as lying in the penalty area. When any part of the ball touches a penalty area, the whole ball is considered to be in that penalty area, so penalty area rules apply.
Why the penalty area wins
The Rules define five areas of the course, and the general area is basically everything that isn't one of the four specific areas: penalty areas, bunkers, putting greens, and the teeing area. Rule 2.2c says a ball can only lie in one area. If part of it is in the general area and part in a specific area, the specific area wins. Since a penalty area is a specific area, it takes precedence over the general area every time.
What this means for your next shot
Because the ball is treated as in the penalty area, you have two main choices. You can play it as it lies with no penalty — grounding your club and taking practice swings are allowed in penalty areas now. Or you can take penalty relief under Rule 17.1d for one stroke: stroke-and-distance, back-on-the-line, or lateral relief (red penalty area only). The fact that part of the ball was touching the general area doesn't give you free relief or change the penalty.
Frequently asked questions
Does it matter how much of the ball is in the penalty area?
No. Even if just a sliver of the ball touches the penalty area, the whole ball is treated as lying in the penalty area.
Can I take free relief because part of the ball is in the general area?
No. The Rules don't give free relief for a ball that's partly in the general area and partly in a penalty area. The penalty area rules apply in full.
What if the ball is touching a penalty area and a bunker at the same time?
The penalty area wins. The order of precedence is penalty area first, then bunker, then putting green.
Can I ground my club if the ball is only barely in the penalty area?
Yes. Since the ball is treated as in the penalty area, you may ground your club, take practice swings, and remove loose impediments just like anywhere else in a penalty area.
What if I'm not sure whether the ball touches the penalty area line?
If it's not clear, the benefit of the doubt goes to the player — but only if the ball is not clearly in the penalty area. When in doubt, treat it as in the general area until you can confirm it touches the penalty area.