Alphabetical means arranged in the order of the alphabet, from A to Z. When a list is in alphabetical order, all items starting with A come first, then B, then C, and so on. If multiple items start with the same letter, you look at the second letter to decide which comes first (so “apple” comes before “arrow”).

You use alphabetical order constantly without even thinking about it. Dictionaries arrange words alphabetically so you can find them quickly. Libraries organize fiction books alphabetically by the author's last name. Your teacher might take attendance alphabetically, calling students by last name from Anderson to Zhang.

Before computers, keeping things alphabetical required careful work. Librarians used card catalogs with thousands of entries filed alphabetically. Encyclopedia companies had to figure out where to add new entries when they updated their volumes. Today, computers can sort thousands of items alphabetically in seconds, but the system itself is ancient and has been around for over 2,000 years, making it one of humanity's most useful organizational tools.