The drop looks like a clear yet falls just behind the net. Learn to disguise it, slow the racket at contact and practise with targets instead of feel.
The honest answer: The drop is an overhead stroke that looks like a clear but brings the shuttle only softly over the net, where it falls steeply. The opponent stands at the back, expects a long shuttle and has to come far forward. When the deception works, it is one of the most effective strokes in the game.
That the drop lives on deception is well documented. In a study with 16 players, the experts read serves from the movements of shoulder, elbow, wrist and racket and were right more often than novices [1]. The study looked at serves, not drops, but the principle is the same: whoever shows what is coming loses the element of surprise.
Honestly, there is hardly any research on the drop itself. Whatever carries no [n] is coaching practice. And it is worth having a secure clear before you tackle the drop: the drop builds exactly on it.
Run sideways under the shuttle and take the racket behind your head as for the clear. The key point: preparation and arm position are identical to the clear. A study with 29 players showed that the position of your body relative to the shuttle directly influences the launch angle [2]. So stand cleanly under the shuttle.
Hit the shuttle in front of the shoulder. Just before contact you let the racket speed drop, the forearm brakes. The shuttle gets little speed and flies on a short trajectory. The whole movement stays fluid; only the last part becomes soft.
Milestone: The shuttle falls behind the net in the front third of the opponent's court.
Tilt the racket face slightly so the shuttle slides forward and down (slice drop). That makes it even shorter and harder to read. For the start the straight drop is enough; add the slice only once the straight drop works.
Place a towel just behind the net. Play ten drops and count the hits. Target shots are not a luxury: in a study with 16 players (on the backhand jump smash, so transferable only by analogy), shots to a target affected the landing differently from pure shadow play, and the authors considered target practice more effective [4].
Milestone: Seven of ten drops land in the front third.
Do not let your partner know what is coming. Switch randomly between clear and drop and ask whether he recognised it beforehand. Novices can learn to see through deception better when training strips out distracting details and shows only the basic movement [3]. So you can learn to read your opponent too.
Do the video experiment: film yourself from the side playing a clear and a drop. Put both clips next to each other and ask yourself: can I see the difference before the moment of contact? If so, your preparation is not identical. Pause the picture just before contact and compare elbow height and racket position.
An overhead stroke in which the shuttle falls softly over the net and lands just behind it. It starts like a clear but is slowed at contact. It forces the opponent forward and lives on deception.
Prepare drop and clear with exactly the same movement and decide only at contact. Experts read shots from shoulder, elbow, wrist and racket [1]. If your arm looks the same, your opponent cannot read what is coming.
When the opponent is at the back and you have time to get into a clean position under the shuttle. It is an attacking stroke between clear and smash. This is coaching practice. Under time pressure the clear is safer.
Usually you brake too early or too much. Hit the shuttle higher and further forward and brake only just before contact. Practise with a target, not only in shadow play (transferred from a jump-smash study) [4]. That gives you a feel for the right dosage.
The drop is an overhead stroke from the back court, the net shot a soft stroke from the front court. Both end just behind the net. The drop uses clear-style deception and needs the way back, while the net shot focuses on precision and early contact.
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