Cross-Sell

Cross-selling is a sales technique used to get a customer to spend more by purchasing a product that’s related to what’s being bought already.

It's different from “upselling,” where a vendor tries to get you to buy the more expensive model of a car, for example. Cross-selling is more like “Don’t you want some fries to go with that burger?” Or, “That dress would look spectacular with these sandals.” How about “This toy does not come with batteries; would you like to purchase them now?”

Amazon does this all the time with their “frequently bought together” suggestions on every product page.