Step 1: Recall the definition:
Sales organisation is the process of making goods move from the seller to the buyer. The exchange must suit both sides.
Step 2: Find the two parties:
One party is the marketer, who sells the goods. The other party is the customer (buyer or consumer), who pays and uses the goods.
Step 3: Complete the sentence:
The sentence becomes: Sales organisation involves transfer of goods on terms satisfactory to both the marketer and the customer.
This shows that a sale is fair only when both sides gain.
Final Answer:
The missing word is customer (the buyer).