Alphabetizer

The options, and when each matters

• Ignore case — on by default. Off, you get an ASCII-style sort where every capital precedes every lowercase letter, so Zebra comes before apple. That is occasionally what you want and almost never what you expected.
• Remove duplicates — compares by the same rule as the sort, so with "ignore case" on, "Apple" and "apple" count as one item.
• Ignore leading A, An, The — the library convention. Sorts "The Hobbit" under H while still printing the article.
• Natural number order — compares digit runs numerically, so Chapter 2 comes before Chapter 10 instead of after it.
• Reverse — Z to A. Applied after everything else.

Sorting is not one thing

"Alphabetical order" hides several genuinely different rules, and they disagree on real data. A phone book, a dictionary, a bibliography and a programming language's default sort will each order the same hundred names slightly differently — over capitals, over spaces inside names, over accented characters, over whether "McDonald" files as written or as "MacDonald".

The defaults here match what most people mean by the phrase: case-blind, accent-aware, spaces significant. Where your context has a stricter convention — a citation style, a catalogue standard — check the result against it rather than assuming.