Recently I was looking through the titles of books and once again came across the different spelling of the of preposition.

2009. Clean Code: A Handbook of Agile Software Craftsmanship. 
2011. The Clean Coder: A Code Of Conduct For Professional Programmers. 

As you can see above, the two books have different spellings of the preposition: of and Of, respectively.

Can you please explain to me the difference between using the preposition of with a capital letter and the lower/uppercase letter form? What is the logic or grammar behind it? Does it depend on the context?

  • It's not a different spelling, just a different convention for capitalisation. Commented Aug 4, 2021 at 20:28

3 Answers 3


There is no difference, it is the same word in broadly the same context.

Words in a title, such as a book title, are usually capitalised. There are no strict rules about this, but most 'style-guides' (manuals produced for professional writers and academics to ensure uniformity) say you should capitalise the first and last words of any title, and any other words except articles, prepositions and coordinating conjunctions. So, most people would NOT capitalise 'of' (unless it was the first word, for example, 'Of Mice and Men'), but style-guides are just guides, not rules.

It is worth noting that articles and prepositions are often left out of initialisms - for example, the 'RSPB' is the Royal Society for the Protection of Birds. However, sometimes words like articles and prepositions are deliberately left in to make a more pleasing acronym that can be pronounced, so this can be another reason why a title may capitalise words normally left uncapitalised. Also, your title includes the term 'code of conduct' which is sometimes abbreviated in isolation as 'COC'.

  • 1
    Ok, I think I understand it: style-guides are just guides, not rules. From books titles: TAOCP, SICP and HTDP is examples of it. Commented Aug 26, 2021 at 13:00

The 2009 title is formatted correctly.

The 2011 title is formatted incorrectly according to every style guide I know. AND it is not the way the actual book is printed, as you can see at Amazon.

A preposition or article that does not begin a title should begin with a lowercase letter. Many style guides (for example, APA) make an exception for words that follow a colon. So the A that follows the colon in your example is correctly capitalized.

Note that for should follow the same rule and begin with a lowercase f.

Some style guides also make an exception for long prepositions, such as "without."

Wikipedia is crowd-sourced. It contains errors.

  • That is, am I correct in assuming that the rule is: if a preposition is not at the beginning of a sentence, it is ALWAYS written in uppercase form? Commented Aug 4, 2021 at 9:22
  • 2
    No. I have edited my answer to clarify the point. Commented Aug 4, 2021 at 9:35

Academic writers, journalists, book authors, and website content writers have to follow a style guide recommended by a professor, book/journal publisher, newspaper, or website owner.

A lot of book and journal publishers recommend formatting the draft as per the American Psychological Association (APA) or Modern Language Association (MLA) style guides. Moreover, most journalists follow Associated Press (AP) Stylebook guide.

The APA, MLA, and AP style guides recommend capitalization of the first and last words in headings and titles as well as nouns, pronouns, verbs, adverbs, and adjectives.

APA and AP recommend the use of lowercase for articles, prepositions and conjunctions that are three or fewer words in a heading/title, such as of, to, the, and, etc.

MLA rules are different in that lowercase must be used for both short and long prepositions and conjunctions that are more than three words like between and against.

In the end, remember that there are no hard and fast rules regarding headings and titles. The preposition in both the titles you have mentioned mean the same thing. You can write headings/titles in either lowercase or uppercase. But you must be consistent in your formatting.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .