Slice
The shot starts near your target line, then curves hard to the right and lands well short of a normal drive.
Why it happens
A slice happens when the clubface is open relative to the direction the club is travelling (the swing path) at the moment of impact. The bigger that gap between face and path, the more sidespin gets put on the ball, and the more it curves, usually while also losing distance because the spin axis is tilted instead of upright.
Possible causes in your swing, and how to fix each one
Tap any cause to see its fix. Work through them one at a time, usually one or two are the real culprit.
1Grip is too weak
If your left hand is rotated too far toward the target on the handle, the clubface naturally wants to stay open through impact, no matter how good the rest of the swing is.
2Swinging out-to-in across the ball
When the clubhead approaches from outside the target line and cuts across to the inside, it adds left-to-right sidespin on top of any face issue, which is the classic "over the top" slice move.
3Clubface staying open through impact
Even with a good path, if your forearms and wrists don't rotate the toe of the club past the heel through the hitting area, the face arrives open.
4Ball position too far forward
Playing the ball off the front foot means the club is already moving toward the left of target by the time it arrives, which encourages the out-to-in path.
5Rushing the transition with the upper body
If the shoulders and arms start the downswing before the lower body, the club gets thrown outside the ideal plane, which is a common source of the over-the-top move.
When to stop self-diagnosing
If you've genuinely worked through two or three of these causes over several range sessions and the miss keeps showing up, that's not a failure since it usually means the real cause is something you can't feel or see in your own swing. A single 30-minute lesson with a certified instructor, who can watch you hit balls, will find it faster than any website. Bring this page along and tell them what you've already ruled out; it'll save you both time.