Englishfor English speakers
by
Preposition
—
near or next to.
The mailbox is by the bus stop.
—
at some time before (the given time).
Be back by ten o'clock!
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if something is done by somebody, it is done through their action
The matter was decided by the chairman.
The boat was swamped by the water.
He was protected by his body armour.
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if something is created by somebody, they are the creator, author, etc.
There are many well-known plays by William Shakespeare.
—
shows how someone does something
I avoided the guards by moving only when they weren't looking.
—
using the rules or logic of.
I sorted the items by category.
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with a change of. In this case, by shows how much something has changed.
Our stock is up by ten percent.
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shows how slowly, or how quickly, someone does something (used in the form "X by X" or "by Xs")
We went through the book page by page.
We crawled forward by inches.
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If you multiply mathx/math by mathy/math, you multiply mathx/math × mathy/math.
Five multiplied by seven is 35.
—
If you divide mathx/math by mathy/math, you find how many mathy/maths are in mathx/math.
35 divided by seven is five.
a
Determinative
—
A is used when the following word could be any of a certain type.
Compare "A book I saw on the shelf" and "The book I gave you yesterday".
a
Noun
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A is the first letter of the alphabet.
The letter "a" comes before "b".
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In some schools, an A is a very high grade.
Ron got an A on his earth science test.
narrow
Adjective
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If something is narrow, it is not wide; it is thin.
The bridge was narrow.
She has a narrow waist.
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If something is narrow, it is limited.
He has a narrow knowledge of math.
narrow
Verb
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If something is narrowed, it becomes thinner; it becomes narrower.
He narrowed his eyes in anger.
The road narrows near the lake.
margin
Noun
—
A margin is the space on the sides of a page where there is no writing.
If you own the book, write notes in the margin.
—
A margin is the difference between what the winner has and what the loser has.
The team won every game with an average 24-point victory margin per game.
The Board of Education voted by a narrow margin to accept the new standards.
Mitt Romney is leading in the latest polls by a slim margin, 29 percent of the vote to 's 26 percent.
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A margin is the difference between what a business pays for something and what it sells it for.
The current profit margins on those products run between 55 and 62 percent.
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A margin is extra time, room, money, etc. that you plan for in case something needs more.
There's almost no margin for error with the landing the plane.
The extra fuel that was carried along gave us a bit of a safety margin.
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A margin of error is the amount that the true value varies from the measured value.
The poll had a margin of error of plus or minus 4 percentage points.
We produce these pieced to be 2.5 meters long, with an overall error margin of 1.4 millimeters.
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If somebody is on the margin(s), they are not a central member and have little power.