Thank you for the opportunity to help you with your question!
What does a smaller number of substitutes mean for the slope of the demand curve?
It means that buyers cannot respond quickly to price changes, For this reason, the demand curve is steep.
What about the slope of the demand curve? Define slope.
A slope shows the relationship between the price of goods and the quantity demanded. It therefore describes how the price of the good affects the quantity demanded. With more substitutes, buyers usually respond more to price changes.
Please let me know if you need any clarification. I'm always happy to answer your questions.