English Grammar for Scientific Writers

	SUMMARY OF COMMA USE

SOME PLACES NEVER TO PUT COMMAS

	1.	Never use a comma to separate a verb from its subject or object.

	2.	Never put a comma between two items joined by a coordinating conjunction (and, or, but, for, nor) unless they are (1) part of a longer series or (2) independent clauses.

PLACES WHERE YOU SHOULD PUT COMMAS

	A.	In Series:  Place a comma after each of a series of independent, parallel items except the last.  If the items contain commas, separate them with semicolons instead.

	B.	Between Independent Clauses:  Two independent clauses joined by a coordinating conjunction (and, or, but, for, nor) are separated by a comma, which precedes the conjunction.

	C.	In Conventionally Determined Locations:  In 5‑digit numbers, between coordinates of a point in geometry, after letter salutations and closings, in ellipses.

	D.	To Enclose Parenthetical Material:

	1.	Elaborations on proper nouns (e.g., state names that follow city names, years that follow dates, titles that follow the bearer's name)

	2.	Transitional words and phrases and those introducing examples (e.g., "however," "therefore," "for example")

	3.	Material without grammatical relation to the rest of the sentence (absolutes like nominatives of direct address, nominatives absolute, interjections)

	4.	Direct quotes (when any punctuation is necessary)

	5.	Material moved out of its normal position (e.g., initials that follow the surname, preposed modifier phrases and clauses)

	6.	Nonrestrictive modifier phrases and clauses

	7.	Nonrestrictive appositives