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A comparison forming a compound is not hyphenated except to prevent ambiguity or if in Webster's:
second largest buffalo
            third busiest street
            the best known person
but     third-ranked convention city

Use a comma in such expressions as "The Amazon is the second longest river in the world, after the Nile." Without the comma, the Amazon becomes the third longest river. Include, if possible, the instances that surpass the one cited.

The word times may be used in comparing a large thing with a small one, as in it is three times as large as. The phrase it is three times larger than is ambiguous; it means to some people three times as large as and to others four times as large as. For this reason, it should be avoided.

Do not multiply smallness. Since times implies multiplication, not division or diminution, 1/25,000 as bright is preferred to 25,000 times fainter:
            Incorrect:    twice as small, three times as short, five times thinner than
            Correct:         half as long, a third as tall, a fifth as thin

Avoid "three times fewer" and "three times as few." Write "a third as many."

In credit lines use the average length, height, etc., of the animal or plant shown or a phrase like "six times life-size." In pictures made with an electron microscope, first write magnified 480 times. Thereafter use the times sign: 1,000,000 X.

Write size, not sized: calf-size. Use "actual size," not "life-size," for inanimate things.

Different from: Preferred to different than in virtually every construction:
            Alligators are different from crocodiles, not alligators are different than crocodiles.

However, when the use of "from" would require an elaborate construction (e.g., "from that which"), use "than" or rewrite.

When comparing sizes, specify what measurement is being used:
            Saying "Earth is twice as large as Mars" is true if comparing diameters;
            however, if volume is compared, Earth is about six and a half times as large as Mars.

Be cautious in comparing temperatures: Because zero on the Fahrenheit and Celsius scales is not the same as absolute zero, something with a temperature of 40 degrees is not twice as hot as something at 20 degrees.

See also larger than, SIZE.