Punctuation and Capitalization
Punctuation and Capitalization tests the marks that control meaning and the capital letters that mark names and sentence boundaries.
End marks and sentence boundaries
Every sentence ends with a full stop, question mark, or exclamation mark. Use a question mark for direct questions and a full stop for indirect ones: 'He asked whether we were ready.' Do not join two sentences with a comma alone; use a full stop, a semicolon, or a conjunction.
Commas
Use commas to separate items in a list, after an introductory phrase, around extra non-essential information, and before and/but/so when they join two complete sentences. Do not put a comma between a subject and its verb, or before that in a reported clause.
Apostrophes
An apostrophe shows possession or a contraction. Singular owner: the girl's bag. Plural owners ending in s: the girls' bags. Plural not ending in s: the children's toys. Its means belonging to it; it's means it is. Do not use apostrophes for ordinary plurals: mangoes, not mango's.
Quotation marks, colons, semicolons
Quotation marks enclose a speaker's exact words, with the comma or full stop inside: 'Sit down,' she said. A colon introduces a list or explanation; a semicolon joins two closely related sentences.
Capitalization
Capitalize the first word of a sentence, proper nouns and names, days and months, languages and nationalities, titles before names, and the main words in titles. Do not capitalize seasons, ordinary school subjects (except languages), or compass directions unless they name a region.
Worked example
'the childrens books were left at aunt marys house' becomes 'The children's books were left at Aunt Mary's house.' Reasoning: Capitalize the first word and the proper name; children is already plural, so the possessive apostrophe goes before the s; Mary's needs an apostrophe.
Traps
Missing apostrophes in possessives; putting apostrophes in plurals; capitalizing common nouns; and joining sentences with commas.