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Section 11.8.3.2

Which Article Is Appropriate?

Once you have decided that an article is necessary,you must choose between an indefinite article(a and an) the definite article(the). In general, you should use the definite article if the noun is unique or known to the reader and an indefinitearticle if the noun is one of a group or new to the reader.

Use an indefinite article (a oran) with singular countable nouns torefer to an arbitrary member of a larger group or to introduce a member of thelarger group for the first time. The indefinite article always implies thatother examples of the noun exist.


Unacceptable

Piece of string one light-year long would wrap around the equator of theEarth 236 million times. [Piece is singular and countable, so anarticle (definite or indefinite) must be used.]

Unacceptable

The piece of string one light-year long would wraparound the equator of the Earth 236 million times. [The definite articleimplies that only one piece of string exists or that the author already mentionedthis particular piece of string before.]

Acceptable

A piece of string one light-year long would wrap aroundthe equator of the Earth 236 million times. [The indefinite articleimplies that the author is introducing this particular piece of string, yet otherpieces of string exist.]

--Andrew Fraknoi, "The Universe: An Introduction"


Never use an indefinite article with a pluralcountable noun or with an uncountable noun.


Unacceptable

Unlike a stars, a planets do notshine under their own power, but simply reflect the light of their star.

Acceptable

Unlike stars, planets do not shine under their own power, but simplyreflect the light of their star.

--Andrew Fraknoi, "The Universe: An Introduction"


Use the definite article (the) with singular countable nouns to suggestthat the noun is unique (its group consists of only one member) or to refer toa noun that has been previously introduced. The definite article used witha singular countable noun usually implies that only one example of the nounexists or is relevant to the situation.


The Earth is one of nine planets circlingthe star we call the Sun.

--Andrew Fraknoi, "The Universe: An Introduction"


You can also use the definite article with a singular countable noun to refer tothe entire class that the noun belongs to. This is often done with species ofanimals, inventions, or musical instruments:


The honey possum of Australia is the only mammal thatlives exclusively on nectar.

--"Take It or Leave It," Valley Comic News


Use the definite article with plural countable nouns or uncountable nouns torefer to the entire category in existence or to a specific subset of the categoryas defined by the context.


When particles of matter meet with and annihilate their correspondingparticles of antimatter, the energy produced comes out purelyin the form of gamma rays. [The author used the definite article with theuncountable noun energy to indicate that he was referring to only thesubset of energy that is produced when these particles collide.]

--Harding E. Smith, "Quasars and Active Galaxies"


Do not use the definite article when referring to uncountable nouns or pluralcountable nouns in a general sense.


Unacceptable

The discovery of the pulsars and the efficient way inwhich the pulsars supply energy to thesupernova remnants like the Crab Nebula has led to the suggestion thatthe rapidly rotating, magnetized, massive objects might alsopower the quasars.

Acceptable

The discovery of pulsars and the efficient way in which pulsars supplyenergy to supernova remnants like the Crab Nebula has led to the suggestion thatrapidly rotating, magnetized, massive objects might also power quasars.

--Harding E. Smith, "Quasars and Active Galaxies"


Use the definite article whenever you modify a noun with a superlative adjective (using most orleast with the modifier or adding -est to it), with the wordsame, or with an ordinal number (first, fourth).


Unacceptable

Most common cause of coughing is stress.

Acceptable

The most common cause of coughing is stress.

--"Take It or Leave It," Valley Comic News

Unacceptable

First steam locomotive in regular service was in England in 1814.

Acceptable

The first steam locomotive in regular service was inEngland in 1814.

--"Take It or Leave It," Valley Comic News

Unacceptable

At same temperature and at same level, moist air weighs less than dryair.

Unacceptable

At a same temperature and at a samelevel, moist air weighs less than dry air.

Acceptable

At the same temperature and at thesame level, moist air weighs less than dry air.

--C. Donald Ahrens, Meteorology Today


Always use the definite article before the names of groups of years, such asdecades:


Unacceptable

When fax machines were invented in 1960s, it took an average of 6 minutesto send a one-page document.

Acceptable

When fax machines were invented in the 1960s, it tookan average of 6 minutes to send a one-page document.

--Les Krantz, America by the Numbers


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## Which Article Is Appropriate? ##
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