For capitalization in English, there are three main rules on which everyone can agree:
- Capitalize the first letter in every sentence.
- Capitalize initial letters of proper nouns.
- Capitalize the pronoun I.
Beyond these three uses, there is much disagreement over when to capitalize. Every major publication and publisher has its own standards, and many writers have their own preferences (which are generally overridden by in-house rules during publication).
In modern writing, there are simultaneous trends toward and away from capitalization. The trend in informal writing and much journalistic writing is away from it. Meanwhile, there is an unfortunate trend in business, corporate, and marketing writing to capitalize words for emphasis or to give words a little extra heft. But if you use instant messaging, text messaging, email, or social networking, you’ve probably noticed that many people don’t capitalize at all in these mediums.
Regardless of what writers do in business and marketing (where trying to enforce good writing is a lost cause), the best rule of thumb for capitalization is to err on the side of minimalism. Follow the three rules listed above, avoid capitalizing common nouns just because other people do, avoid capitalization for emphasis (that’s what italicization is for), and never use all caps (LIKE THIS). Beyond those guidelines, here are a few other points:
- Different publications have different standards for capitalizing titles and headings. Use what looks best to you.
- Complete sentences within sentences should be capitalized. This includes quoted sentences (e.g., She said, “How are you?”) and complete sentences following colons (e.g. One thing’s for sure: You’ll get your money’s worth).
- In abbreviations, capitalize letters that stand for capitalized words (e.g., USMC for United States Marine Corp, BoA for Bank of America).
- Some great 19th-century poets had a habit of capitalizing abstract and personified nouns such as Nature and Love, but that doesn’t make it a good idea in general.