British English and American English
There are many colours to consider: red, blue, green, yellow and orange.
There are many colours to consider: red, blue and green are all bold choices.
There are many colours to consider: colour is an important aspect of interior décor which you should never overlook.
There are many colours to consider: Colour is an important aspect of interior décor which you should never overlook.
Some style guides suggest that in American English, the first letter following a colon should only be capitalised if there are two related sentences after the colon.
There are many colours to consider: Red, blue and green are all bold choices. Colour is an important aspect of interior décor which you should never overlook.
5. Scientific animal and plant names
The scientific names for animals and plants are derived from Latin and should be written per Latin capitalisation rules. A scientific name may be a binomen (generic name plus specific name) or a trinomen (generic name plus a specific name plus a subspecific name).
In each case, only the generic name should be written in title case.
The scientific name for the domestic cat is Felis catus whereas the scientific name for a tiger is Panthera tigris. The scientific name for the Siberian tiger is Panthera tigris tigris.
Lavender (Lavandula) smells simply wonderful. The most widely cultivated species is Lavandula angustifoli.
6. The first word of a quote
When a quote is a complete sentence, the first word should be written in title case
When Steve arrived at the house he asked, ”What are we having for dinner tonight?”
When the words in quotation marks are only a partial quote or do not form an autonomous sentence, the first word should not be written in title case.
Steve said he was “really angry” about the cancellation.
Steve described the dog as being “quite large and muscular but very friendly.”
7. Days, months and holidays
Days, months and specific holidays are proper nouns and so must be written in title case.
Steve’s anniversary is in December, shortly before Christmas. He generally celebrates on the nearest Saturday, rather than on the day itself.
The seasons of the year are not proper nouns and so the first letters of these words should not be capitalised.
I prefer walking in spring because it can be too hot in the summer months.
8. Films, books and TV series
Style guides vary in the advice they give regarding the titles of movies, books, TV programmes and other artistic works. The general rule is that you should capitalise the first letter of all nouns, verbs and adjectives. The first word in a title should always be written in title case, whatever type of word it is. Articles, prepositions and conjunctions should not be written in title case unless they are the first word. However, some style guides suggest that conjunctions and prepositions that are longer than five letters should be written in title case.
I really enjoyed reading A Tale of Two Cities.
I loved reading The Curious Incident of the Dog in the Night-Time
Did you see the movie From Russia with Love?
9. Periods, eras and events
You should treat specific periods of time, eras and historic events as proper nouns. Each word should be written in title case. However, centuries are not presented in title case.
The period between 4000BC and 2000BC is referred to as the Bronze Age.
I have fond memories of the Swinging Sixties.
The 20th century was an era of rapid technological advancement.
10. Closing a letter or email
When closing a written communication, you will generally use a valediction. You should use title case for the first word and lower case for all subsequent words.
The rules of capitalisation in English are so complex that even the most dedicated grammar pedant can slip up from time to time. Animal breed names appear to cause the most confusion, to the extent that the incorrect use of title case has become the norm. But with a little care and attention, you can write correctly. Just be prepared to defend your use of German shepherd and cocker spaniel!
One final point to note. Capitalisation is the correct spelling in British English. When writing in American English, use capitalization!