Exercise and assignment are not the same thing

These two words describe one event from opposite sides, and using them interchangeably makes it impossible to reason about who controls what.

Exercise is the holder invoking their right. It is an action, taken deliberately, by the party who paid the premium. Assignment is the writer being told they must now perform. It is not an action; it is something that happens to them, and they have no say in whether or when.

The mechanism connecting them is worth knowing because it explains a common surprise. When a holder exercises, the instruction goes to the clearing organisation, which selects among the accounts holding the corresponding short position. Selection is by a defined allocation procedure, commonly random or pro rata. So being assigned is not a signal about your specific position; it means the allocation landed on you.

One more piece: automatic exercise. At expiry, in-the-money contracts are generally exercised automatically by the clearing process above a small threshold, which means a holder who forgets about a contract still gets the transaction, and a writer who assumed nothing would happen still gets assigned. A holder who does not want that outcome must generally submit contrary instructions before the deadline.

Notice how the vocabulary maps onto the asymmetry from lesson one. Exercise is a verb the long side owns, and it is the thing the premium bought. Assignment is a verb applied to the short side, and accepting it is what the premium was payment for. If you find yourself saying that you were exercised, or that you assigned an option, the sentence has lost track of who held which half of the contract — and that is usually the same confusion that makes the risk of a short position hard to see clearly.

A third term completes the set. Closing a position is neither exercise nor assignment: it is a new trade in the opposite direction that cancels the existing one. A holder who wants out generally closes rather than exercises, because exercising abandons any remaining extrinsic value. A writer who wants out closes too, which is the only action available to them, because they cannot decline an assignment once it arrives.