Updates 2024/01/25

Recently, I am re-reading one of the most famous book on English writing, Elements of Style, which is written by William Strunk. I still remember my feelings when I first read this book during my PhD, roughly 2015. I was shocked to know about the new world of English writing! I wished I had known this book in the first year I learnt English, which was 2001.

This book is so informative that I can’t remember all the rules all the time. Not surprising though, the shortest pencil is better than the longest memory. Therefore, I am trying to summarise the key rules in this book using my own language and examples.

This post is about when commas should and should not be used within a sentence. It summarises Rule 2,3,4,5,6 in the book.

In a series of three or more terms, using a comma after each term except the last

red, white, and blue

He opened the letter, read it, and made a note of its contents

Exception: In the names of business firms the last comma is ommitted Brown, Shipley & Co.

Extraordinary situation: what if some terms contain ‘and’ or commas? The solution is using semicolons to replace commas.

Incorrect: I love apples and oranges, peanut butter and jelly, and bananas.

Correct: I love apples and oranges; peanut butter and jelly; and bananas.

Enclose parenthetic expressions between commas

This is to make sure the rhythm of the sentence is reasonable. If the interruption to the flow of the sentence is but slight, the writer may safely omit the commas. But whether the interruption be slight or considerable, he must never insert one comma and omit the other.

Here, commas must come in pair.

The best way to see a country, unless you are pressed for time, is to travel on foot.

He saw us coming, and unaware that we had learned of his treachery, greeted us with a smile.

Strict cases: always to be enclosed between commas or between comma and period

  1. the year, when forming part of a date, and the day of the month, when following the day of the week

    February to July, 1916.
April 6, 1917.

  2. the abbreviations etc. and jr.

  3. non-restrictive relative clauses, which do not serve to identify or define the antecedent noun, and similar clauses introduced by conjunctions indicating time or place. How do you know whether a relative clause is non-restrictive? If the clause be removed and the sentence still makes sense, the clause is non-restrictive.

    The audience, which had at first been indifferent, became more and more interested.
   
The candidate who best meets these requirements will obtain the place. [This is restrictive relative clause, as the clause introduced by who does serve to tell which of several possible candidates is meant]
   
Nether Stowey, where Coleridge wrote The Rime of the Ancient Mariner, is a few miles from Bridgewater.

Place a comma before a conjunction introducing a co-ordinate clause

As the early records of the city have disappeared, the story of its first years can no longer be reconstructed.

Although the situation is perilous, there is still one chance of escape.

Or the subordinate clauses might be replaced by phrases:

Owing to the disappearance of the early records of the city, the story of its first years can no longer be reconstructed.

In this perilous situation, there is still one chance of escape.

Two-part sentences of which the second member is introduced by as (in the sense of because), for, or, nor, and while (in the sense of and at the same time) likewise require a comma before the conjunction.

Complicated case: there is a if clause after but

The situation is perilous, but if we are prepared to act promptly, there is still one chance of escape.

Do not join independent clauses by a comma

Three approaches for joining independent clauses:

Approach 1

Stevenson's romances are entertaining; they are full of exciting adventures.

It is nearly half past five; we cannot reach town before dark.

Approach 2

Stevenson's romances are entertaining. They are full of exciting adventures.

It is nearly half past five. We cannot reach town before dark.

Approach 3

Stevenson's romances are entertaining, for they are full of exciting adventures.

It is nearly half past five, and we cannot reach town before dark.

Approach 1 is better than #2 and #3, as it suggests the close relationship between the two statements (compared to #2) and is briefer and therefore more forcible (compared to #3)。

Two exceptions to this rule: if the clauses are very short, and are alike in form, a comma is permissible

Man proposes, God disposes.

The gate swung apart, the bridge fell, the portcullis was drawn up.

The second exception is the colloquial form of expression, which is inappropriate in writing.

Do not break sentences into two

Do not use periods for commas. Counter examples are:

I met them on a Cunard liner several years ago. Coming home from Liverpool to New York.

He was an interesting talker. A man who had traveled all over the world and lived in half a dozen countries.

These sentences can be rewritten:

I met them on a Cunard liner several years ago, coming home from Liverpool to New York.

He was an interesting talker, a man who had traveled all over the world and lived in half a dozen countries.

Examples from GIS textbook

Here are some relevant examples from the preface of the famous GIS textbook, Geographic Information Systems and Science. These sentences are excellent examples that use commas and semicolons; they are also brief and forcible.

Digital geographic information is central to the practicality of GIS. If it does not exist, it is expensive to collect, edit, or update. If it does exist, it cuts cost and time.

We have variously, both alone and in collaboration, spent much of our careers researching and writing about geographic information.

We go far beyond how to choose, install, and run a GIS; that is only one part of the enterprise.

Fundamentally, GIS is an application-led technology, yet successful applications need appropriate scientific foundations.

The field of geographic information systems, GIS, is concerned with the description, explanation, and prediction of patterns and processes at geographic scales.

Reference

  • Strunk, W. and White, E. B. (1999) The elements of style. Boston: Allyn and Bacon.

  • Longley, P. et al. (2015) Geographic information science and systems. Third edition. Hoboken, NJ: Wiley. Available at: https://books.google.co.uk/books?hl=en&lr=&id=C_EwBgAAQBAJ&oi=fnd&pg=PA39&dq=geographic+information+system+science+2015&ots=r5Kz-w-_NL&sig=6TTlkTP3kU6AUgnWBTarm5fWZ_s (Accessed: 12 December 2018).