Punctuation is grammar made visible. At an expert level it is not decoration but a system of signals with near-grammatical rules.
The comma
Where commas are required
After most introductory elements: (Very short openers may drop it: )
Around non-defining relative clauses and other parentheticals:
Between items in a series: — on the serial (Oxford) comma, see below.
Before a coordinator joining independent clauses:
Between coordinate adjectives: (test: works) — but not cumulative ones: .
After a quotation before the tag:
Where commas are forbidden
Between subject and verb:
Between verb and object: (no comma before an indirect -clause)
Around defining relative clauses: means all students cheat.
Splicing two sentences: the — Repair with a full stop, semicolon, coordinator, or subordinator: (Literary exceptions — — are deliberate and rhythmic.)
The () is house style at most American publishers and at Oxford; most British newspapers omit it. Use it consistently, and always insert it when omission creates ambiguity:
The semicolon and the colon
Semicolon joins two closely related independent clauses: Also separates list items that contain commas:
Colon introduces what fulfils the promise of the first clause — a list, an explanation, a quotation, an elaboration: What precedes a colon must be able to stand alone: \(\to\) drop the colon or rewrite ().
Capital after a colon: BrE lowercase; AmE often capitalizes a full sentence after the colon. Be consistent.
Dashes, parentheses, hyphens
The em dash (—) sets off interruptions with emphasis: BrE often prefers a spaced en dash (–) for the same job. Limit to one pair per sentence.
Parentheses whisper what dashes shout: asides the reader may skip. Punctuation goes outside unless the whole sentence is parenthesized. (Like this.)
The en dash (–) marks ranges and connections: .
The hyphen (-) binds compounds. Hyphenate compound modifiers before a noun: — but not after: ; and never with adverbs: \(\to\) . Distinguish (cover again) from ; from .
The apostrophe
Possession: singular ; regular plural ; irregular plural ; classical names ending in allow or .
Contractions: (= it is/has), (= who is), .
Never for plurals: \(\to\) .
The possessive pronouns have none: .
Time and money possessives: .
Quotation marks
AmE: double quotes, commas and periods inside: BrE: often single quotes, punctuation placed by logic:
Question and exclamation marks go inside only if they belong to the quotation: vs.
Scare quotes signal distance — use sparingly:
Restrictive punctuation as meaning
Punctuation changes truth conditions. Classic contrasts:
(all) vs. (some)
vs.
vs.
(she stayed — anger was the reason) vs. (ambiguous: perhaps she left for another reason)
Exercises
Punctuate Insert all necessary punctuation.
after the merger was announced the share price which had been falling for months doubled
the recipe calls for flour butter sugar and three large eggs
there was only one problem nobody had tested the parachute
my brother who lives in oslo is visiting my sister lives here
its been a year since the company lost its licence
Comma splice repair Repair each splice in two different ways.
The deadline passed, nobody had submitted anything.
She is a brilliant negotiator, her deals prove it.
Hyphenation Add or remove hyphens as required.
a well respected twenty year old critic
the strategy was ill conceived but the ill conceived plan succeeded anyway (fix both halves)
a quickly-assembled team of highly trained engineers
they signed a five year, thirty million dollar contract
Meaning by punctuation Explain the difference in meaning within each pair.
(a) The staff, who joined after 2020, get no bonus. (b) The staff who joined after 2020 get no bonus.
(a) She said the manager is lying. (b) She, said the manager, is lying.
(a) Re-sign the contract. (b) Resign the contract… I mean, resign from the post.