rule_04.dita

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<concept id="concept_cfx_gt4_z2b">
    <title>Rule 4</title>
    <shortdesc>Place a comma before a conjunction introducing a co-ordinate clause.</shortdesc>
    <conbody>
        <lq> The early records of the city have disappeared, and the story of its first years can no
            longer be reconstructed.</lq>
        <lq>The situation is perilous, but there is still one chance of escape.</lq>
        <p>Sentences of this type, isolated from their context, may seem to be in need of rewriting.
            As they make complete sense when the comma is reached, the second clause has the
            appearance of an afterthought. Further, <i>and</i> is the least specific of connectives.
            Used between independent clauses, it indicates only that a relation exists between them
            without defining that relation. In the example above, the relation is that of cause and
            result. The two sentences might be rewritten:</p>
        <lq>As the early records of the city have disappeared, the story of its first years can no
            longer be reconstructed.</lq>
        <lq>Although the situation is perilous, there is still one chance of escape.</lq>
        <p>Or the subordinate clauses might be replaced by phrases:</p>
        <lq>Owing to the disappearance of the early records of the city, the story of its first
            years can no longer be reconstructed.</lq>
        <lq>In this perilous situation, there is still one chance of escape. </lq>
        <p>But a writer may err by making his sentences too uniformly compact and periodic, and an
            occasional loose sentence prevents the style from becoming too formal and gives the
            reader a certain relief. Consequently, loose sentences of the type first quoted are
            common in easy, unstudied writing. But a writer should be careful not to construct too
            many of his sentences after this pattern (see <xref keyref="rule_14"
            >Rule 14</xref>).</p>
        <p>Two-part sentences of which the second member is introduced by <i>as</i> (in the sense of
                <i>because</i>), <i>for</i>, <i>or</i>, <i>nor</i>, and <i>while</i> (in the sense
            of <i>and at the same time</i>) likewise require a comma before the conjunction.</p>
        <p>If the second member is introduced by an adverb, a semicolon, not a comma, is required
            (see <xref keyref="rule_05">Rule 5</xref>). The connectives <i>so</i> and <i>yet</i> may
            be used either as adverbs or as conjunctions, accordingly as the second clause is felt
            to be co-ordinate or subordinate; consequently either mark of punctuation may be
            justified. But these uses of <i>so</i> (equivalent to <i>accordingly</i> or to <i>so
                that</i>) are somewhat colloquial and should, as a rule, be avoided in writing. A
            simple correction, usually serviceable, is to omit the word <i>so</i> and begin the
            first clause with <i>as</i> or <i>since</i>:</p>
        <table outputclass="example" id="table_uvy_5j3_z2b">
            <tgroup cols="2">
                <colspec colname="col1"/>
                <colspec colname="col2"/>
                <tbody>
                    <row>
                        <entry morerows="0" namest="col1" nameend="col1" outputclass="first">I had
                            never been in the place before; so I had difficulty in finding my way
                            about.</entry>
                        <entry morerows="0" namest="col2" nameend="col2" outputclass="second">As I
                            had never been in the place before, I had difficulty in finding my way
                            about.</entry>
                    </row>
                </tbody>
            </tgroup>
        </table>
        <p>If a dependent clause, or an introductory phrase requiring to be set off by a comma,
            precedes the second independent clause, no comma is needed after the conjunction.</p>
        <lq>The situation is perilous, but if we are prepared to act promptly, there is still one
            chance of escape. </lq>
        <p>When the subject is the same for both clauses and is expressed only once, a comma is
            required if the connective is <i>but</i>. If the connective is <i>and</i>, the comma
            should be omitted if the relation between the two statements is close or immediate.</p>
        <lq>I have heard his arguments, but am still unconvinced. He has had several years'
            experience and is thoroughly competent. </lq>
    </conbody>
</concept>