Skilful and correct use of punctuation helps clarify thinking and improves written (and spoken!) English for native and non-native users alike.
An apostrophe is used either to signify possession or to indicate one or more missing letters. It never helps form a plural.
“John’s book” is correct: the apostrophe is showing possession. Note that when a word ends with an s, the s following the apostrophe is omitted when showing possession: Callas’ book, not Callas’s book.
In “The bird completed it’s journey” the use of an apostrophe with the adjective its is incorrect: the bird may possess the journey, grammatically (it is the bird's journey) but it's only ever means it is and never shows possession.
“It’s about time we stopped” is correct: the apostrophe shows a letter (i) has been omitted from the verb it is.
“I'd like to go now.” Here, the apostrophe indicates (four) omitted letters from the verb I would.
The similarity in appearance of the adjective its and the verb it's causes confusion. The former only ever shows possession; the latter, being simply an abbreviated form of the verb it is, can never indicate possession.
The apostrophe never indicates a plural
“The LEDs are bright red” not “The LED's are bright red”.
Brackets, round ( )
Round brackets (also known as Parentheses) are used to add an explanatory or qualifying note or remark within a sentence, but, crucially, in the context of the current topic or idea being written about.
“The protesters were arrested (but not convicted) for disturbing the peace.”
“His favourite jacket (the Tweed one) was ruined in the ensuing fight.”
Sometimes that explanatory or qualifying note consists of a whole sentence, in which case the entire sentence (beginning with a capital letter and ending with a full stop) should be inside the brackets.
Because brackets constitute a break in the reading flow, a comma that would otherwise be needed immediately following them is rarely necessary. Also see 'Brackets, square' below.
Brackets, square [ ]
Similar in appearance to round brackets, they have the specific function of showing text that has been added by someone such as an editor (usually not the original author or speaker) to help clarify the sense or meaning of quoted words.
“He [pointing to the accused] was the one who did it!”
“It [paper] is great for linear information.”
Modern American usage of 'brackets' usually refers to square brackets, whereas in Britain parentheses/round brackets are usually meant.
It has three uses: to introduce a list of objects or ideas, to indicate that an explanation is being given, or to indicate that a summary of something is now being given.
“You will need the following: a box of paper, a pencil, a ruler…”
“We soon solved the mystery of the missing book: it had fallen behind the desk.”
“As the climbers reached the mountain top they enthusiastically hugged and embraced each other: they were overjoyed to be there.”
Note that because the colon, semi-colon and comma all signify a pause that is shorter than a full stop, and that only words following a full stop have an initial capital (apart from proper names, such as London, which must always have one) the word immediately following each of these punctuation marks must not begin with a capital letter. There is, however, one exception: if a sub-heading ends with a colon, the following text should begin with a capital letter.
Finally, when introducing a quotation that can stand on its own as a complete thought, a colon rather than a comma is often used.
The comma has numerous uses:
1. When two independent clauses (clauses that contain both a subject and a verb and could therefore stand as separate sentences) are linked by a conjunction, the conjunction is preceded by a comma:
“She went to the market, and she bought some apples.”
If the second clause does not have its own subject, but depends for its subject on the first one, it is not independent and so the rule does not apply:
“She went to the market and bought some apples.”
2. A clause that contains both a subject and an object, but cannot stand on its own, is dependent on what follows to complete it. It must therefore be followed by a comma in order to introduce the completing clause. In the following example, When she was at the market… is a dependent clause.
“When she was at the market, she saw some pears.”
(“For a child to be born a mother and a father are required.” A comma after the dependent clause For a child to be born is needed to make clear that the sentence is not saying a child is born a mother.)
3. Commas are needed for appositives (two or more words or phrases that refer to the same entity and are grammatically parallel). Here, she and my sister are in apposition as they refer to the same person and are in the same grammatical relation to the rest of the sentence:
“When she was at the market, she, my sister, saw some pears.”
However, if a phrase gives essential information no comma is needed:
“She bought some oranges before she saw some pears.”
4. Commas are needed to separate listed items:
“When she was at the market, she, my sister, bought some oranges before seeing pears, mangos, bananas, cherries and grapes nearby.”
5. A comma is needed after an introductory adverb:
“Slowly, she made her way around the market.”
6. Quoted speech needs a comma to introduce it and the single quotation mark goes inside the full stop:
“When she was at the market, she phoned saying, 'I'll be back soon'.”
If the attribution comes after the quote, the comma goes inside the quotation marks:
“I'll be back soon,” she said.
7. When a sentence begins with a yes or a no, follow it with a comma.
“Yes, she has gone to the market.”
8. Use a comma when directly addressing someone:
“Anne, are you too going to the market?”
9. Put a comma between two or more coordinate adjectives that modify the same noun or noun phrase:
“She had recently been to the small, friendly, local fish market.”
Adjectives are coordinate if their places in the sentence can be swapped without affecting meaning. Non-coordinate adjectives don't need a comma:
“She had been to the local fish market.” Here, local qualifies the noun phrase fish market and does not coordinate with another adjective.
10. Commas help offset a negation:
“She had been to the local market, not to the edge-of-town supermarket.”
11. Use a comma to show a distinct shift in thought process is occurring in a sentence:
“The rumoured closure of the market was unpopular, especially with the stall-holders.”
12. Dates need commas too:
“Saturday, 17th July, 2016, is the closure date.”
13. Commas are needed as an aid to clarity before every sequence of three numbers.
For example: 6,000 or 2,650,488
14. Since the purpose of language is clear communication, prevention of ambiguity must be the overriding consideration in the debate about the Oxford comma (a comma before and).
It is used (often for rhetorical reasons) to introduce an important and relevant aside into the current sentence, just as one might make a point in conversation. It can occur in the middle or at the end of a sentence.
“Either we follow his lead or we don't—I think we should—but we need to be consistent about it.”
“He got up, dusted himself off and walked sorely to the door—the end, it seemed, of his reign as office bully.”
Ellipsis (plural: ellipses) comes from a Greek word meaning omission or falling short. It refers to the intentional omission of one or more words from a phrase, sentence or piece of text. It's shown in punctuation by a series of dots (typically three) that appears in place of the missing word(s).
“The suggestions weren’t long in coming… ”
It may also be used to indicate a pause or to show emphasis in a sentence. “He tried… and tried… to make himself heard.”
Exclamation Mark !
This mark is used after words or phrases or sentences that are exclamatory or exhortatory.
An exclamation is typically a cry or shout that expresses an emotion: “We won!” However, it can be quieter than that and yet still express strong feelings: “Never was there a better chance!”
An exhortation is an urging or encouraging word (or words) that may be spoken softly, loudly or shouted: “Come on, you can do it!”
Full Stop .
A full stop signals the end of a sentence. It therefore separates or distinguishes one sentence from another.
Hyphenation aims to bring clarity and efficiency to writing by preventing confusion and the wasting of time and effort working out likely meanings.
Its most mundane use is at the very end of a line of text to indicate that a lack of space has created an incomplete word whose remainder begins the next line.
In addition to this merely functional role it also has an important one in clarifying meaning. For example, no one is different from no-one.
“There was no one thing that caused the rift between them: it was several things.”
“No-one knew the way she felt.”
No-one refers only to people (no single person); no one without the hyphen refers to no single entity (no one cause, no one item, no one way, etc).
The hyphen also has an important role in compound adjectives; without it the meaning is changed, sometimes considerably.
“He was an ill prepared student.” Was he ill and yet prepared (for the exam) or was he just ill-prepared (poorly prepared)?
“His father was a blue collar worker.” Did he (sadly) make collars for a living; were they always blue ones? The term blue-collar worker is sometimes used to refer to someone who wears a uniform at work or who does manual work, in contrast to a white-collar worker (who does neither).
“The book is up to date” is correct and so is, “He had an up-to-date book.” In the former, the phrase is not an adjective; in the latter it is.
In addition to compound adjectives, hyphens are also used to create numbers e.g. twenty-three; to create compound nouns e.g. father-in-law, T-shirt; and with prefixes and suffixes to modify nouns e.g. ex-employee, self-knowledge, president-elect, etc.
Question Mark ?
Without this mark the reader can be left unsure whether a word, phrase or sentence is a statement or question.
“She will be back soon.”
“She will be back soon?”
The first sentence is a statement of fact (or, at least, a report of an intention). The second is a request for information, expressed as a question. The difference in meaning and function is achieved solely by the presence or absence of a question mark.
Quotation Marks ”
Single quotation marks ' ' have three uses:
1. To distinguish a topic. For example: “I can never remember how to spell 'indigenous'.”
2. To highlight a word or phrase in order to make a point. Here, the point is irony: “She had a visit from her 'friend' Alice.”
3. To quote within a quotation. For example: “She then said 'I will not!' and ran away.”
Double quotation marks “ ” are to be used only for direct speech. When giving the title of a book, poem or event, use italics. The following examples illustrate most scenarios. Notice, in particular, where the commas and full stops are placed.
“I'm ready and I hope you are too.”
When a complete sentence is given in quotation marks, the full stop comes inside them.
She said “I'm ready and I hope you are too”.
Notice how this differs from the previous sentence. Since it includes quoted speech, the full stop goes outside the quotation mark, not before it. This is because, instead of saying She said she's ready and hopes you are too the speaker actually quotes her words, and so they fall within his sentence.
“I'm ready”, she said, “and I hope you are too.”
The first comma should be outside the double quotation mark, as shown.
“I'm ready”, she said. “Will he be ready soon?”
Since she began a new question, a full stop is needed to close the previous sentence and a capital letter is needed for will.
He said “I will be ready soon”.
Notice that there is no comma after said and the full stop goes after the final quotation mark, not before it. Why? Because the sentence is not different (in terms of construction) from He said he will be ready soon.
He remarked: “I think she said 'I am ready'.”
When quoted words include a quotation, use single quotation marks. Notice that the full stop goes between the mark that signals the end of the quoted sentence and the double quotation mark.
When a quotation runs uninterruptedly over more than one paragraph, begin each with a double quotation mark, but end only the last paragraph with a double quotation mark.
It is used in two ways:
1. Separating two independent clauses or ideas of similar importance in a sentence, often replacing conjunctions such as and or but, sometimes achieving a dramatic effect. Note that in each of these examples the writer could have used two separate sentences, but chose not to in order to smooth the flow of the writing since the two ideas are closely related.
“He shook open the bag; a snake fell out.”
“The view is fine; the poor weather is what is restricting visibility.”
“The tyrant dies and his rule is over; the martyr dies and his rule begins.” Soren Kierkegaard
2. Semi-colons are used to help clearly differentiate items in complex lists:
“The party consisted of Bill, the leader; Anne, the doctor; John, the engineer; Phil, the navigator;…”
“They visited Edinburgh, Glasgow and Dundee in Scotland; Swansea, Cardiff, Carmarthen and Newport in Wales; and Halifax, Leeds and York in England.”