Improved

Contemporary physics is still exploring neutron stars, black holes, and the penetration of electrons through potential barriers.

4. Coordinate Modifiers

A comma is used between coordinate modifiers. Modifiers are coordinate if they modify the same word. You can test to see if the modifiers are coordinate by inserting and between them. If the description still makes sense, then the modifiers are coordinate:

Ebola viruses are known as filoviruses for their long, filamentlike appearance under a microscope. [Long and filamentlike modify the appearance of the virus equally, so a comma is needed between them.]

5. Non-defining Modifiers

Commas are used to set off non-defining (nonrestrictive) modifiers. A non-defining modifier is usually introduced by which / who and contains information that is not essential to establishing the meaning of what it modifies. Note that you have to use which or who, but not that in these sentences. That can be used in defining relative clauses, and there is no comma:

Brass, which is an alloy of copper and zinc, is used to make bolts and screws.

The experiments that were described in the previous section were part of a series that was conducted over a range of mode mixes.

6. Parenthetic Elements

Commas are used to set off parenthetic elements (for example, apposition – to provide extra, supporting or explanatory information about a term, in parenthesis, linking words and phrases):

ASHRAE, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers, Inc., lists the following job titles that technicians and technologists may qualify for.

Oppenheimer became known, of course, for leading the physicists who built the atomic bomb at Los Alamos Laboratory.

On the other hand, the chances of success are great.

The chemical engineer's greatest contribution, however, will be in the development of new energy systems.

7. Elliptical Constructions

A comma is used to indicate the omission of a word or words readily understood from the context:

In the United States there are ninety-two scanners; in Europe, eighty-five; in all of Africa, six. [The commas indicate the omission of the words there are.]

8. Specialized Uses of Commas

- In numbers with five or more digits, Anglo-American usage dictates that there be commas before groups of three digits, counting from the right, except for a group of three digits at the beginning of the number:

Customers reported a total of 212,413 hardware malfunctions.

- Commas are used to separate adjacent numbers:

In 1994, 212 cases had been diagnosed.

- Commas are used to separate items in an address:

Einstein then moved to Princeton, New Jersey.

- Commas are used to set off the year in dates expressed in the month-day-year sequence:

Greenberg began the project on July 2, 1992.

Commas should be omitted when only the month and the year are stated:

Greenberg began the project in July 1992.

In dates written in the day-month-year sequence, the comma is omitted:

Greenberg began the project on 2 July 1992.

- In formulas (chemical: use commas to separate letters and numbers identifying the location of an atom or group in a molecule): [2,3-³H]serine

Superfluous Commas

Except after an introductory dependent clause, do not use a comma to separate a dependent clause from a main clause unless the dependent clause provides nonessential information:

Incorrect

Ever since the atomistic view of matter came to be accepted, it has been a burning question, how to see into the microworld of molecular chemistry.

Correct

Ever since the atomistic view of matter came to be accepted, it has been a burning question how to see into the microworld of molecular chemistry.

Do not set off a clause that is essential to the sentence. Such clauses often begin with that:

Incorrect

Systematic surveys of the ocean floor revealed, that there were submarine mountain ranges, that extended for thousands of kilometers.

Correct

Systematic surveys of the ocean floor revealed that there were submarine mountain ranges that extended for thousands of kilometers.

Do not use a comma to separate the subject from the rest of the sentence.

Incorrect

A biosensor that produces a changing electrical signal in response to levels of glucose in the bloodstream of diabetics, could be used to control the release of insulin so as to maintain the concentration of blood sugar at a steady, safe level.

Correct

A biosensor that produces a changing electrical signal in response to levels of glucose in the bloodstream of diabetics could be used to control the release of insulin so as to maintain the concentration of blood sugar at a steady, safe level.

Placement of Commas with Other Punctuation

Commas are placed inside quotation marks but outside parentheses:

The University classified the study as an "experiment," which doubled the time needed for approval by the Committee on Research.

The manual contains a lengthy, though incomplete (and somewhat obscure), description of the compiler.

3.4 Colons

Colons are used for the following purposes:

- to introduce and emphasize lists, quotations and explanations and certain appositional elements;

- to express ratios;

- to separate numbers signifying different nouns, such as in separating units of time or elements in a bibliographic citation;

- to separate titles from subtitles

To set off and emphasize lists, colons are often preceded by a word like namely, such as, as follows, the following, etc.

Anyone communicating via computer needs a security system that ensures three essential requirements: confidentiality, authentication, and trust.

or

Anyone communicating via computer needs a security system that ensures three essential requirements:

• confidentiality

• authentication

• trust

(Begin each element of lists, series, or phrases with lowercase letters).

To set off and emphasize quotations (colons are placed outside quotation marks):

The contract reads: "DL-400 coaxial cable shall be used for all platform instrument installations at Site 5, unless a specific exception is justified in the approved work order."

Kulik noted: "Even potatoes are probably much better guarded today than radioactive materials."

To set off and emphasize explanations and appositional elements:

In designing the tachometer, the team first posed a question: What operations are needed on the input signal in order to generate the desired output?

The projects have, however, been able to measure the effects of caloric restriction on so-called biomarkers of aging: attributes that generally change with age and may help predict the future span of health or life.

To express ratios:

The ratio of drag torque to friction torque cannot exceed 3:1.

To separate units of time:

The main thruster engines ignited at 7:05 a.m.

The Mar 16 03:21:44 1995

To separate elements in a citation (in certain documentation styles):

E. F. Lyon, "Airport Surface Traffic Automation," Lincoln Laboratory Journal 4:151 (1991).

3.5 Semicolons

Semicolons are used:

a) to join two independent clauses (the semicolon is weaker than a full stop, but stronger than a comma. So, it can be used to join two independent but closely related sentences):

The system has three beam launchers; two are in the two-tube combiner, and one is in the OP receiver.

Two independent clauses are never linked with just a comma; this is known as a comma splice error:

Incorrect

In 1931 Oppenheimer attempted to find an equation for the photon that would be an analogue to Dirac's equation for the electron, he failed in this effort.

A comma splice error can be corrected in four ways:

- by separatinge the independent clauses into two separate sentences and punctuating both sentences with periods.

Correct

In 1931 Oppenheimer attempted to find an equation for the photon that would be an analogue to Dirac's equation for the electron. He failed in this effort.

- by replacing the comma with a semicolon or with a semicolon and a conjunctive adverb such as however or furthermore. (The conjunctive adverb is then normally followed by a comma.)

Correct

In 1931 Oppenheimer attempted to find an equation for the photon that would be an analogue to Dirac's equation for the electron; he failed in this effort. [or ". . . electron; however, he failed . . ."]

- by replacing the comma with a comma and a coordinating conjunction.

Correct

In 1931 Oppenheimer attempted to find an equation for the photon that would be an analogue to Dirac's equation for the electron, but he failed in this effort.

- by making one of the clauses into a subordinate clause.

Correct

Although in 1931 Oppenheimer attempted to find an equation for the photon that would be an analogue to Dirac's equation for the electron, he failed in this effort.

b) to separate parts of a sentence that have commas in it:

Italicize titles of journals, books, newsletters, and manuals; letters, words, terms, and equation symbols; foreign words; and names of specific vessels.

3.6 Question Marks

A question mark is used (in scientific writing they are often rhetoric questions):

1) to end an interrogative sentence:

Have past efforts to develop an AIDS vaccine been based on the wrong approach?

2) to indicate uncertainty about data:

The first synthesis was accomplished by Claude Poux (1810?-1897).

3.7 Exclamation Points

In technical and scientific writing, exclamation points are used only to end warning or caution statements or as specialized scientific notation. For other purposes, a period or question mark is used.

WARNING!

Place the power supply latch in the locked position before plugging in the device! Failure to lock the power supply latch may result in severe injury!

CAUTION!

Do not continue if there are any files on the disk you wish to keep! The format procedure will destroy all files stored on the disk.