The textbook also gives al-mushtari, meaning either a purchaser or Jupiter, the planet. A buyer is a party to a transaction, while the planet is an astronomical body; these meanings are fundamentally different.
“The purchaser paid the price” — the transactional setting identifies the buyer.
“Jupiter is a planet” — the astronomical setting identifies the planet.
These are explanatory examples. Contextual indications help select the intended sense of a shared expression.