‘In an alphabetical order’ vs. ‘in alphabetical order’ in English

by Jakub Marian

Tip: See my list of the Most Common Mistakes in English. It will teach you how to avoid mis­takes with com­mas, pre­pos­i­tions, ir­reg­u­lar verbs, and much more.

The word “order” is usually treated as an uncountable (mass) noun, which means that it is normally not combined with an indefinite article. For example, one would normally say:

correct The dictionary lists all entries in alphabetical order.
unnatural The dictionary lists all entries in an alphabetical order.
unnatural The dictionary lists all entries in the alphabetical order.

The second and third example above would make sense if there were several types of alphabetical order (for example, lexicographers could argue whether a special character like “Ç” goes between “C” and “D” or at the end of the dictionary, giving two possible alphabetical orders). Unless you are a linguist or lexicographer, it is unlikely you will ever need to say “an alphabetical order” or “the alphabetical order”.

The same applies to various other kinds of order, such as “ascending order” and “descending order”. Again, there is no need to use an article, unless you are a mathematician working with several types of ascending/descending order:

correct The values are listed in ascending/descending order.
unnatural The values are listed in an ascending/descending order.

By the way, if you haven’t read my guide on how to avoid the most common mistakes in English, make sure to check it out; it deals with similar topics.