Alphabetic order

Alphabetical order is a system whereby strings of characters are placed in order based on the position of the characters in the conventional ordering of an alphabet. It is one of the methods of collation.

To determine which of two strings comes first in alphabetical order, their first letters are compared. If they differ, then the string whose first letter comes earlier in the alphabet comes before the other string. If the first letters are the same, then the second letters are compared, and so on. If a position is reached where one string has no more letters to compare while the other does, then the first (shorter) string is deemed to come first in alphabetical order.

Capital letters (upper case) are generally considered to be identical to their corresponding lower case letters for the purposes of alphabetical ordering, though conventions may be adopted to handle situations where two strings differ only in capitalization. Various conventions also exist for the handling of strings containing spaces, modified letters (such as those with diacritics), and non-letter characters such as marks of punctuation.

The result of placing a set of words or strings in alphabetical order is that all the strings beginning with the same letter are grouped together; and within that grouping all words beginning with the same two-letter sequence are grouped together; and so on. The system thus tends to maximize the number of common initial letters between adjacent words.

Alphabetical order was first used in the 1st millennium BCE by Northwest Semitic scribes using the Abjad system. The first effective use of alphabetical order as a cataloging device among scholars may have been in ancient Alexandria. In the 1st century BCE, Roman writer Varro compiled alphabetic lists of authors and titles. In the 2nd century CE, Sextus Pompeius Festus wrote an encyclopedic epitome of the works of Verrius Flaccus, De verborum significatu, with entries in alphabetic order. In the 3rd century CE, Harpocration wrote a Homeric lexicon alphabetized by all letters. In the 10th century, the author of the Suda used alphabetic order with phonetic variations. In the 14th century, the author of the Fons memorabilium universi used a classification, but used alphabetical order within some of the books.

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