| Figures
Never start a sentence with a figure; write the number in words instead.
Use figures for numerals from 11 upwards, and for all numerals
that include a decimal point or a fraction (eg, 4.25, 4).
Use words for simple numerals from one to ten, except: in references
to pages; in percentages (eg, 4%) and in sets of numerals, some
of which are higher than ten, eg, Deaths from this cause in the
past three years were 14, 9 and 6.
It is occasionally permissible
to use words rather than numbers when referring to a rough
or rhetorical figure (such as a thousand curses).
Fractions should be hyphenated (one-half, three-quarters, etc)
and, unless they are attached to whole numbers (8, 29), spelled out in words, even when the figures are higher than ten: He gave a tenth of his salary to the church, a twentieth to his mistress and a thirtieth to his wife.
Do not compare a fraction with a decimal (so avoid The rate
fell from 3% to 3.1%).
Fractions are more precise than decimals (3.14 neglects an infinity of figures that are embraced by 22/7), but your readers probably do not think so.
You should therefore use fractions for rough figures (Kenya's
population is growing at 3% a year, A hectare is 2 acres) and decimals for more exact ones: The retail price index is rising at an annual rate of 10.6%.
But treat all numbers with respect; that usually means resisting
the precision of more than one decimal place, and generally favouring
rounding off. Beware of phoney over-precision.
Use m for million, but spell out billion-which means 1,000m-except in charts, where bn is permissible but not obligatory. Thus: 8m, 8m,
8 billion, DM8 billion.
A billion is a thousand million, a trillion a thousand
billion, a quadrillion a thousand trillion.
Use 5,000-6,000, 5-6%, 5m-6m (not 5-6m) and 5 billion-6 billion.
But sales rose from 5m to 6m (not 5m-6m); estimates ranged
between 5m and 6m (not 5m-6m).
Where to is being used as part of a ratio, it is usually best
to spell it out. Thus They decided, by nine votes to two, to
put the matter to the general assembly which voted, 27 to 19,
to insist that the ratio of vodka to tomato juice in a bloody
mary should be at least one to three, though the odds of this
being so in most bars were put at no better than 11 to 4.
Where a ratio is being used
adjectivally, figures and hyphens may be used, but only if one
of the figures is greater than ten: thus a 50-20 vote, a 19-9
vote. Otherwise, spell out the figures and use to: a two-to-one
vote, a ten-to-one probability.
Do not use a hyphen in place of to except with figures: He received
a sentence of 15-20 years in jail but He promised to have escaped
within three to four weeks. With figures, use a person or per
person, a year or per year, not per caput, per capita or per
annum.
In most contexts that are not American or British, prefer
hectares to acres, kilometres (or km) to miles, metres to yards,
litres to gallons, kilos to lb, tonnes to tons, Celsius to
Fahrenheit, etc. Regardless of which you choose, you should give
an equivalent, on first use, in the other units:
It was hoped
that after improvements to the engine the car would give 20km
to the litre (47 miles per American gallon), compared with
its present average of 15km per litre.
Remember that in few countries
do you now buy petrol in imperial gallons.
In America it is sold in American gallons;
in most other places it is sold in litres.
The style for aircraft
types can be confusing. Some have hyphens in obvious places
(eg, F-22, B-2 bomber), some in unusual places (MiG-31M) and
some none at all (Airbus A340, BAe RJ70). Others have both
name and number (Lockheed P-3 Orion). When in doubt, use Jane's "All The World's Aircraft". Its index also includes
makers' correct names.
The style for calibres is 50mm or 105mm with no hyphen, but
5.5-inch and 25-pounder.
Use the sign % instead of per cent.
But write percentage, not %age (though in most contexts proportion
or share is preferable). A fall from 4% to 2% is a drop of
two percentage points, or of 50%, but not of 2%.
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