SAT grammar rules

A semicolon does the same job as a period, and the test will never make you choose between them.

Both put a full stop between two complete sentences. If a question offers you both, neither is the answer — look at the other two choices.

• ✓Correct:The kiln reached 1,200 degrees. The glaze fused in under an hour.
• ✓Correct:The kiln reached 1,200 degrees; the glaze fused in under an hour.

Two complete sentences joined by only a comma is always wrong.

The giveaway is a comma followed by a pronoun — it, they, she, he, we. Cover the comma and read on: if what follows could stand alone, the comma cannot hold it.

• ✕Incorrect:The alloy resists corrosion, it was developed for marine fittings.
• ✓Correct:The alloy resists corrosion; it was developed for marine fittings.

A comma plus and, but, or, so, yet, for or nor can join two complete sentences.

This is the third way to do the same job as a period. The conjunction has to be there; the comma alone is a splice.

• ✓Correct:The survey ran for three seasons, but the final year was never published.

Do not put a comma before and or but when the second half has no subject of its own.

Test it by replacing the comma and the conjunction with a period. If the second half is not a sentence, the comma was wrong.

• ✕Incorrect:The glacier retreated through the 1990s, but has held its position since.
• ✓Correct:The glacier retreated through the 1990s but has held its position since.

A colon or a dash introduces a list or an explanation, and what comes before it must be a complete sentence.

What comes after can be a full sentence or a fragment — that is the difference from a semicolon, which needs a complete sentence on both sides.

• ✕Incorrect:The vault holds three kinds of: seed, spore and tuber.
• ✓Correct:The vault holds three kinds of material: seed, spore and tuber.

A colon and a single dash do the same job, and the test will never make you choose between them.

Same reasoning as the semicolon and the period. If both appear among the choices, the answer is one of the other two.

• ✓Correct:One factor decided it: the clay was local.
• ✓Correct:One factor decided it — the clay was local.

If two choices do exactly the same job, cross out both.

A question cannot have two right answers. So when a period and a semicolon sit between the same two sentences, or a colon and a dash sit in the same place, neither is the answer and you are really choosing between the other two. This is the fastest elimination on the section.

• ✓Correct:Offered 'kiln.' and 'kiln;' with nothing else changed, cross out both.
• ✓Correct:Offered 'decided it:' and 'decided it —' with nothing else changed, cross out both.

Two things stop that elimination: a list, and any other change in the choice.

A semicolon also separates the items of a long list when the items already contain commas, and a period cannot do that — so there a semicolon can be right with a period beside it. And if switching the mark also switches a pronoun, a transition or a capital letter, the two choices are no longer doing the same job, so check them separately.

• ✓Correct:the lower weir, which floods each spring; the mill race, disused since 1962; and the upper cut
• ✓Correct:'seam. However,' against 'seam; however,' — the capital changed too, so compare them properly

When a complete sentence stands on each side, a colon, a dash, a semicolon and a period are all correct.

So a question like that has no single answer, and you will not be given one. If you ever seem to be choosing between two of these marks with full sentences on both sides, re-read — one side is probably not a complete sentence.

• ✓Correct:The frame never shaded the lower canvas: the varnish there yellowed first.
• ✓Correct:The frame never shaded the lower canvas; the varnish there yellowed first.

A clause starting with although, because, when, while, since, until, before or after is not a sentence; when it comes first, it takes a comma.

• ✕Incorrect:Because the resin cures under ultraviolet light the workshop has no windows.
• ✓Correct:Because the resin cures under ultraviolet light, the workshop has no windows.

Information you could lift out of the sentence is marked at both ends, with two commas, two dashes or two parentheses.

Two of the same mark. Mixing them — a dash at one end and a comma at the other — is one of the commonest wrong answers.

• ✕Incorrect:The estuary, which freezes most winters has supported eider since at least 1890.
• ✕Incorrect:The estuary — which freezes most winters, has supported eider since at least 1890.
• ✓Correct:The estuary, which freezes most winters, has supported eider since at least 1890.

Never put a comma immediately before an opening parenthesis.

• ✕Incorrect:The mill, (rebuilt twice) still turns on the original axle.
• ✓Correct:The mill (rebuilt twice) still turns on the original axle.

A name in the middle of a sentence takes either no commas or two. One comma before it is always wrong.

Read the sentence with the name removed. If it still makes sense, the name is extra and takes two commas; if it stops making sense, the name is doing necessary work and takes none.

• ✕Incorrect:The dig was led by the field archaeologist, Nadia Oyelaran, for six seasons.
• ✓Correct:The dig was led by the field archaeologist Nadia Oyelaran for six seasons.

Never put a comma between a subject and its verb, however long the subject is.

• ✕Incorrect:The only bridge still carrying traffic across the lower gorge, was finished in 1931.
• ✓Correct:The only bridge still carrying traffic across the lower gorge was finished in 1931.

No comma before or after a preposition — of, to, by, from, for, with, in, on, at.

• ✕Incorrect:She is among the most cited geologists, of her generation.
• ✓Correct:She is among the most cited geologists of her generation.

No comma between two things joined by and when they are not two sentences.

Same test as before: swap the comma and "and" for a period and see whether you get two sentences. If you do not, drop the comma.

• ✕Incorrect:The collection holds prints, and drawings from the same workshop.
• ✓Correct:The collection holds prints and drawings from the same workshop.

No comma before or after the word that — and none where that has been left out but is understood.

• ✕Incorrect:The timber, used for the piles had to resist waterlogging.
• ✓Correct:The timber used for the piles had to resist waterlogging.

Commas separate items in a list, and separate two adjectives whose order you could swap.

If you can put and between the adjectives, or reverse them, they take a comma. If you cannot, they do not.

• ✓Correct:The seams were dry, brittle and easy to lift.
• ✓Correct:It is a dense, fine-grained limestone.
• ✕Incorrect:It is a dense, grey limestone block.

On a noun, an apostrophe means possession. No apostrophe means plural.

One owner: apostrophe then s. Several owners ending in s: s then apostrophe. An irregular plural that does not end in s takes apostrophe then s, like any singular.

• ✓Correct:the kiln's flue — one kiln
• ✓Correct:the kilns' flues — several kilns
• ✓Correct:the children's drawings — irregular plural

When two nouns in a row are both being tested, the first usually takes the apostrophe and the second does not.

The first noun is possessing the second, so the second is just a plural.

• ✓Correct:the surveyors' notebooks

On a pronoun it is the other way round: no apostrophe means possession. It's only ever means it is.

Read the choice out as it is. If the sentence breaks, you want its. There is no such word as its'.

• ✕Incorrect:The glacier has lost most of it's lower tongue.
• ✓Correct:The glacier has lost most of its lower tongue.
• ✓Correct:The glacier is retreating, and it's doing so faster each decade.

Their is possession, they're is they are, there is a place.

• ✓Correct:The divers logged their ascent times.
• ✓Correct:They're the only team to have surveyed the wreck twice.

Whose is possession; who's only ever means who is. Whose can own things as well as people.

• ✓Correct:a workshop whose records survive in full
• ✓Correct:the conservator who's rebuilding the frame

Match the pronoun to the noun it replaces: a thing takes it, several things take they.

Find the noun first, then choose. It is frequently in the previous sentence, which is why reading only the underlined line is not enough.

• ✕Incorrect:She is known for the murals. It drew on local pigment traditions.
• ✓Correct:She is known for the murals. They drew on local pigment traditions.

For one unnamed person the test uses he or she, not they.

This is narrower than ordinary modern English, where singular they is perfectly normal. The test does not use it, so do not pick it.

• ✓Correct:Each apprentice sharpens his or her own tools.

Who is for people, which is for things.

• ✕Incorrect:the engineer which designed the span
• ✓Correct:the engineer who designed the span

Whom immediately before a verb is wrong; whom after a preposition is right.

• ✕Incorrect:the engineer whom designed the span
• ✓Correct:the engineer to whom the design is credited

Cross out everything between the subject and the verb, then read them together.

What usually sits in between is a phrase starting with of, in, from, for or with, or a description set off by commas. Neither can contain the subject.

• ✕Incorrect:The spread of invasive mussels through the inland lakes have slowed.
• ✓Correct:The spread of invasive mussels through the inland lakes has slowed.

Two subjects joined by and are plural.

• ✕Incorrect:The flue and the firebox was relined in the same year.
• ✓Correct:The flue and the firebox were relined in the same year.

Each and every are singular, however many things follow them.

• ✕Incorrect:Each of the four kilns were fired twice a season.
• ✓Correct:Each of the four kilns was fired twice a season.

A group, a team, a government or a company is singular.

• ✓Correct:The survey team publishes its findings every autumn.

Occasionally the verb comes before its subject. Find the subject anyway.

• ✓Correct:Beneath the floor lie the original timber piles.

Match the tense of the verbs in the sentences before and after.

A paragraph in the past stays in the past. Elaborate tenses — will have gone, would have done — are almost never the answer.

• ✕Incorrect:She trained as a chemist. Her later work is shaped by that training.
• ✓Correct:She trained as a chemist. Her later work was shaped by that training.

For and since mean has or have plus the verb.

They describe something that started in the past and is still going on.

• ✕Incorrect:The lighthouse is automated since 1987.
• ✓Correct:The lighthouse has been automated since 1987.

A finished action with a date takes the simple past.

• ✕Incorrect:She has published the atlas in 1964.
• ✓Correct:She published the atlas in 1964.

By the time means had plus the verb.

Otherwise the simple past and had done are usually both fine, and you will not be asked to choose.

• ✓Correct:By the time the vault opened, the first deposits had already been catalogued.

When the choices are in different tenses, check the number first.

Often only one choice agrees with the subject, and the tenses are there as cover.

• ✓Correct:the accounts that have survived — accounts is plural, so have

Everything in a list takes the same grammatical form.

• ✕Incorrect:The method is quick, repeatable and it costs little.
• ✓Correct:The method is quick, repeatable and cheap.

Certain pairs must be completed: either…or, neither…nor, not only…but also, as…as, more…than.

And what follows each half has to match in form.

• ✕Incorrect:The tram runs either on rails and along the street.
• ✓Correct:The tram runs either on rails or along the street.

A description at the start of a sentence must be followed immediately by the thing it describes.

Ask who or what the opening phrase is about, then check that this is the next thing named.

• ✕Incorrect:Trained as a chemist, the atlas was her first independent work.
• ✓Correct:Trained as a chemist, she produced the atlas as her first independent work.

Compare a thing to a thing, not to the person who made it.

That of and those of are the usual way to fix this, and a possessive apostrophe is the other.

• ✕Incorrect:Her early drawings are better known than Hokusai.
• ✓Correct:Her early drawings are better known than those of Hokusai.
• ✓Correct:Her early drawings are better known than Hokusai's.

Number, many and fewer go with things you can count; amount, much and less go with things you cannot.

• ✕Incorrect:less samples
• ✓Correct:fewer samples

Cover the transition, read both sentences, and say in your own words how the second relates to the first.

There are only three answers worth having: the same direction, the opposite direction, or a result. Then pick the word that says that.

• ✓Correct:same direction — in addition, moreover, for example, in fact
• ✓Correct:opposite — however, nevertheless, in contrast
• ✓Correct:result — therefore, consequently, thus

If two choices mean the same thing, neither is the answer.

A question cannot have two right answers, so a pair like therefore and consequently rules both out.

However, therefore and moreover at the front of a clause need a full stop or a semicolon before them, and a comma after.

• ✕Incorrect:The seam is thin, however, it runs for two kilometres.
• ✓Correct:The seam is thin; however, it runs for two kilometres.

A single word dropped into the middle of a sentence takes two commas.

• ✕Incorrect:The seam is thin. It does, however run for two kilometres.
• ✓Correct:The seam is thin. It does, however, run for two kilometres.

A question mark goes only on a real question. A question folded into a statement takes a full stop.

• ✓Correct:The experiments all test one thing: how do infants judge distance?
• ✓Correct:The experiments all test how infants judge distance.

Could have, should have, would have, might have — never could of.

• ✕Incorrect:The flue could of been relined earlier.
• ✓Correct:The flue could have been relined earlier.