4.13 Items in a Series and Nonrestrictive Elements

Two High-Frequency Punctuation Skills

Items in a series: The student will correctly use, recognize, and correct inappropriate uses of punctuation (commas and sometimes semicolons) to separate items in a series.

Nonrestrictive and parenthetical elements: The student will correctly use punctuation (commas, parentheses, dashes) to set off nonrestrictive and parenthetical sentence elements, as well as recognize and correct cases in which restrictive or essential sentence elements are inappropriately set off with punctuation.

Note the second statement runs in both directions: adding punctuation where it belongs and removing it where it does not.

Part One: Items in a Series

The Basic Pattern

Three or more parallel items take commas:

✓ The survey measured soil density, moisture retention, and root depth.

The comma before and is the serial or Oxford comma. The College Board uses it, and answer choices reflect that convention, so include it.

Two items take no comma:

✓ The survey measured soil density and moisture retention. ✗ The survey measured soil density, and moisture retention.

Semicolons in Complex Series

When the items themselves contain commas, commas alone become unreadable. Semicolons take over as the top-level separator:

✗ The team included Reyes, a hydrologist, Chen, a structural engineer, and Okafor, a soil scientist.

Six commas — is that three people or six? Repair:

✓ The team included Reyes, a hydrologist; Chen, a structural engineer; and Okafor, a soil scientist.

Now the structure is unambiguous. This is the one context in which a semicolon separates items that are not independent clauses, and it is a frequently tested exception.

Superfluous Commas in Series

A comma does not belong before the first item or after the last:

✗ The survey measured, soil density, moisture retention, and root depth. ✗ Soil density, moisture retention, and root depth, were all recorded.

The second is the more insidious error: it separates a compound subject from its verb. Never place a comma between a subject and its verb.

Coordinate vs. Cumulative Adjectives

Adjectives modifying the same noun sometimes take a comma and sometimes do not.

Coordinate adjectives independently modify the noun — comma required:

✓ a thorough, well-documented review

Cumulative adjectives build on each other — no comma:

✓ a standard steel flange

Two tests, and coordinate adjectives pass both:

1. Can you insert and between them? thorough and well-documented ✓ / standard and steel ✗
2. Can you reverse them? well-documented, thorough ✓ / steel standard ✗

Part Two: Restrictive and Nonrestrictive Elements

The Core Distinction

Restrictive (essential): identifies which one. Removing it changes what the sentence is about. No punctuation.

✓ The engineers who signed the report were subpoenaed.

Only the signing engineers were subpoenaed. The clause narrows the group.

Nonrestrictive (non-essential): adds information about an already-identified referent. Set off with paired punctuation.

✓ The engineers, who signed the report, were subpoenaed.

All the engineers were subpoenaed, and incidentally they all signed.

The two sentences differ only by commas, and they mean different things. This is why the punctuation decision is a meaning decision, and why these items are more than mechanical.

The Deletion Test

Remove the element. If the sentence still identifies the same specific thing, the element is nonrestrictive and needs punctuation. If the sentence becomes vague or over-broad, it is restrictive and takes none.

My colleague Dana Whitfield chaired the panel.

Remove Dana Whitfield: My colleague chaired the panel. If I have several colleagues, the name identifies which — restrictive, no commas. If I have exactly one colleague, the name is extra — nonrestrictive, commas.

Context decides. Proper nouns following a unique descriptor are typically nonrestrictive:

✓ The district's only hydrologist, Dana Whitfield, chaired the panel.

Only makes the referent unique, so the name is supplementary.

That and Which

In American usage:

• that introduces restrictive clauses — no comma.
• which introduces nonrestrictive clauses — comma required.

✓ The report that the committee commissioned was released Tuesday. (identifies which report) ✓ The report, which the committee commissioned, was released Tuesday. (one report; the commissioning is extra)

A comma before that is essentially always wrong; which without a comma is usually wrong.

Paired Punctuation Must Match

When a nonrestrictive element interrupts a sentence, it needs punctuation on both sides, of the same kind:

✗ The proposal, submitted in March — was rejected in May. ✗ The proposal submitted in March, was rejected in May. ✓ The proposal, submitted in March, was rejected in May. ✓ The proposal — submitted in March — was rejected in May. ✓ The proposal (submitted in March) was rejected in May.

A mismatched pair is one of the easiest errors to spot once you look for it: find the opening mark, then check that its partner matches.

The three enclosing devices differ in emphasis:

Appositives

An appositive renames a nearby noun and follows the same rules:

✓ The lead investigator, a former state geologist, testified for three hours. (nonrestrictive) ✓ The novelist Ursula Chen testified. (restrictive — identifies which novelist)

Scanning Habits

• Whenever you meet a comma before and, count the items.
• Whenever a series item contains its own comma, expect semicolons.
• Whenever you meet a clause opening with who, which, or that, run the deletion test.
• Whenever you find one comma mid-sentence, look for its partner.