[化学論文のための英語講座] 第68回：読点

(English version is here.)

読点（コンマ）の役割は読みやすい、より明確な文章を作ることです。英語では読点の使い方は日本語の読点とだいたい同じですが、英語ではもっと多彩で、使い方によって意味が変わってしまうこともあります。読点はよく使用されているので、誤用も多いです。読点に関する規則は多いですが、重要なのは以下の三つです。

I 列記

言葉や節を３つ以上つなげる時は読点を利用します。読点が適切かどうかを確認するために、代わりに「and」を使って、文章が正しいかを確かめます。例文を見てみましょう。

1. The isolated solid was characterized by MS, IR, UV-vis and ¹H NMR.
2. The isolated solid was characterized by MS, IR, UV-vis, and ¹H NMR.
3. The isolated solid was characterized by MS and IR and UV-vis and ¹H NMR.

例文３は少しぎこちないですが、１−３のいずれの例文も文法的には正しいです。なお２の UV-vis の後の読点は、Oxford comma または serial comma と呼ばれています。今回の例文1、2では、文章の意味は同じですが、この読点があるかないかによって、微妙にニュアンスが変わる場合もあります。

名詞の対が一つの主語として表される場合は一つの言葉として扱います。そうしないと意味が不明確になります。「and」の有無も重要な点です。例文を見てみましょう。

4. The product was characterized by HRMS, IR, UV-vis, and ¹H and ¹³C NMR.
解説：これは正しいです。最後の読点は「UV-vis」の後にありますので「¹H」と「¹³C」は NMR を修飾する一対です。

5. The product was characterized by HRMS, IR, UV-vis, ¹H and ¹³C NMR.
解説：この文では「and」が一つ欠けていますので「¹H」はNMRとつながらないと感じます。

6. The product was characterized by HRMS, IR, UV-vis and ¹H and ¹³C NMR.
解説：この文では読点が一つ欠けていますので「UV-vis」はNMRとつながると感じます。

II 等位接続詞の前

等位で関係のある完全文章を等位接続詞（and, or, nor, but, while, yet）でつなげる時は接続詞の前に読点を置きます。例文を見てみましょう。

1. The solid reagents were purified by recrystallization, while the liquids were purified by vacuum distillation.
2. Liquid helium is replenished manually once a week, and liquid nitrogen is supplied automatically every week.

例文「1, 2」は「読点連結」として知られています。これに対して接続詞がない場合は読点が不適切だと言われています。妥当ではない例文を見ましょう。

3. The organic phase was retained, the aqueous phase was discarded.
4. Flammable liquids are stored in cabinet A, reactive solids are stored in cabinet D.

例文「3, 4」では接続詞がないので読点の代わりにセミコロン「;」または「and」がより適切です。すなわち例文「3, 4」ように完全な文章を読点で繋げないことです。そういう形式がよく現れますが、厳密に考えると誤りです。

「However, therefore, hence, consequently, nevertheless, thus」の前では、読点は利用しないと言われますが、英語を母国語とする人もよく使います。

5. The addition was also attempted in diethyl ether, however higher yields were obtained in tetrahydrofuran.
6. The intermediate was found to be somewhat unstable, thus it was used directly in the next reaction without purification.

例文「5, 6」では「and, or, nor, but, while, yet」はないので正式な文章ではセミコロン「;」が適切です。

III 文の要素を区別する

文の要素を整理してより読みやすい分かりやすい文章を書くために、要素を読点で囲い込みます。例文を見てみましょう。

1. Ferrocene, an air stable compound, can be stored without special precautions.
2. n-Butyllithium, a powerful base, should be stored at low temperature.

例文「1, 2」は読点で囲い込んだ部分を除くと残りは完全文です。そうではない場合には読点を利用しません。「II, III」の例文の違いに注目してください。「II」では関連のある完全文を繋げますが「III」ではコンマに囲まれた修飾要素が完全文に入っています。読点連結ではありません。

次回はコロンとセミコロンについてです。

Comma

The purpose of the comma is to write clear, easily readable sentences. The use of commas in English is largely the same as in Japanese, but in English they are more versatile and meaning can change depending on use. Commas are often used, and thus are often misused. There are numerous conventions regarding commas, but the following three are very important.

I. Listing

A comma is used when joining three or more words or clauses. To confirm whether use is appropriate, replace the comma with and. If the resulting sentence is correct, then use of a comma is correct. Let us look at a few examples.

1. The isolated solid was characterized by MS, IR, UV-vis and ¹H NMR.
2. The isolated solid was characterized by MS, IR, UV-vis, and ¹H NMR.
3. The isolated solid was characterized by MS and IR and UV-vis and ¹H NMR.

Sentence 3 is a bit awkward, but all three sentences are grammatically correct. The comma after UV-vis in sentence 2 is called an Oxford comma or a serial comma. In this example sentences 1 and 2 are identical in meaning, but there are cases in which the presence or absence of this comma can change the nuance of an expression.

When a noun pair expresses a single subject, it is treated as a single word. If this is not done the meaning can become unclear. The presence or absence of and is also an important point. Let us look at a few examples.

4. The product was characterized by HRMS, IR, UV-vis, and ¹H and ¹³C NMR.
Explanation: This is correct. The final comma is after UV-vis, and thus ¹H and ¹³C, as a pair, modify NMR.

5. The product was characterized by HRMS, IR, UV-vis, ¹H and ¹³C NMR.
Explanation: This sentence lacks an and, giving a feeling that ¹H and ¹³C are not connected.

6. The product was characterized by HRMS, IR, UV-vis and ¹H and ¹³C NMR.
Explanation: This sentence lacks a comma, giving a feeling that UV-vis and NMR are connected.

II Before a coordinating conjunction

When using the coordinating conjunctions (and, or, nor, but, while, yet) to join two complete related sentences a comma is use prior to the conjunction. Let us look at some examples.

1. The solid reagents were purified by recrystallization, while the liquids were purified by vacuum distillation.
2. Liquid helium is replenished manually once a week, and liquid nitrogen is supplied automatically every week.

Examples 1 and 2 are known as joining commas. In cases where there is no coordination conjunction, it is thought that a comma is inappropriate. Let us look at some incorrect examples.

3. The organic phase was retained, the aqueous phase was discarded.
4. Flammable liquids are stored in cabinet A, reactive solids are stored in cabinet D.

There are no coordinating conjunctions in sentences 3 and 4, and thus replacing the comma with a semicolon (;) is more appropriate. That is to say, complete sentences are not joined with a comma as in sentences 3 and 4. This form is often seen, but strictly speaking it is incorrect.

It is said that commas should not be used before however, therefore, hence, consequently, nevertheless and thus, but native English speakers often do use them in this manner.

5. The addition was also attempted in diethyl ether, however higher yields were obtained in tetrahydrofuran.
6. The intermediate was found to be somewhat unstable, thus it was used directly in the next reaction without purification.

None of the conjunctions (and, or, nor, but, while, yet) appear in example 5 or 6, and thus in formal writing a semicolon would be appropriate.

III Separating the elements of a sentence

In order to organise the content and write an easily read and understood sentence, elements are enclosed in commas. Let us look at some examples.

1. Ferrocene, an air stable compound, can be stored without special precautions.
2. n-Butyllithium, a powerful base, should be stored at low temperature.

In example 1 and 2, if the element enclosed by commas is removed, a complete sentence remains. If that is not the case commas are not used. Please note the difference between II and III. Two related, complete sentences are connected in II, but in III the modifying element enclosed in commas is part of a complete sentence. This is not a joining comma.

At next time, we will post about Colons and Semicolons.