Including means having as a part of the whole, or taking something into account as part of a larger group. When a teacher says the test covers chapters 1-5, including chapter 3, she's making clear that chapter 3 is part of what you need to study. When a recipe serves eight people, including the cook, it means the cook is one of the eight, not extra.

The word often appears when someone wants to be specific about what's part of a total. If your family is going on vacation, including your grandmother, that tells you she's counted among the travelers. If a museum ticket costs $15, including tax, you know tax isn't extra: $15 is the complete price.

Including helps prevent confusion. Without it, people might wonder: “Is that part of the group or not?” When your teacher assigns homework, including the word problems at the end, you know those problems aren't optional. When a store advertises “everything on sale, including new arrivals,” shoppers know even the newest items have discounted prices.

The opposite would be excluding, which means leaving something out. A pizza “everything, including anchovies” is quite different from “everything, excluding anchovies.”