The key is to remember that a comma separates.
For mailing addresses, the post office prefers no punctuation in the city, state, zip code sequence. A comma between the city and state is acceptable, but no comma separates the state from the zip code.
The post office also prefers the two-letter codes for the states with two (2) spaces before the zip code.
Commas are not inserted in street addresses or years.
When writing narrative involving a city and state/province/parish, a comma separates the larger unit from the city. If the sentence continues, a comma separates the state/province/parish from what follows.
If the narrative also includes a country, the country should be set off with commas.
If including the zip code, do not use a comma before the zip code.
- >He moved to 3015 72nd Street, Omaha, Nebraska, after living in Boise. He was born in Utah.
- (No comma in the house number)
- (City = “Omaha,” comma, state = “Nebraska,” comma. Only city, “Boise,” no comma. Only state, “Utah,” no comma)
- The letter addressed to Washington, DC 20004, was missent to Washington, Arkansas 81862, a week before the hurricane.
- (City = “Washington,” comma, state = “DC,” no comma before zip code, comma)
- (Because “DC” is an acronym for “District of Colombia,” it should not have periods.)
- Kalama, Washington, has a population of 2,344.
- (City = Kalama, comma, state = “Washington,” comma. Number over 999)
- The letter addressed to 15 Nelson Street, London, England, arrived in two days from Melbourne, Victoria, Australia.
- (Address = “15 Nelson Street,” comma, city = “London,” comma, country = “England,” comma. City = “Melbourne,” comma, state = “Victoria,” comma, country = “Australia.”
- Is there really a town named Podunk in Minnesota?
- (city and state not together, so do not separate them with a comma comma)
A comma separates the month and day from the year.
When writing out a date with the month, the day, and the year, put a comma after the day to distinguish between the two numbers, day and year. Unless at the end of a sentence, another comma follows the year.
Because one number follows another using the month-day-year system, a comma which separates the day number from the year number clarifies the date. No comma is needed if using the day first, then the month, then the year or simply the month and year.
- Two numbers together—a comma separates
- USA: July 4, 1976—Month day (comma) year (comma or period if end of sentence)
- Only one number
- The rest of the world: 4 July 1976—Day month year (no commas)
- April 2018—Month year (no commas)
- April 3—Month day (no year, no commas)
- On Independence Day, July 4, 1976, we celebrated 200 years of the birth of this nation.
- (month day, comma, year, comma + the rest of the sentence)
- Her letter arrived August 20, 2018, even though it was postmarked January 12, 2015.
- (month day, comma, year, comma + the rest of the sentence + month day, comma, year, period to mark end of sentence)
- All registered Thoroughbred horses share the same birthday, January 1 of the year of their birth.
- (month and day. No year so no comma.)
- Each year Mexico celebrates the victory over Napoleon’s forces on 5 May 1862.
- (day month year, no commas)
- The monthly amount of rainfall in April 2018 totaled less than an inch.
- (month year, no commas)
- AD is positive (AD 1500 = +1500, our side of year 0).
- BC is negative (1500 BC = -1500, before year 0).
- BCE or B.C.E. (Before Common Era) is also negative (1500 BCE = -1500).
- CE or C.E. (Common Era) is positive, on our side of history (1500 CE = +1500).
- AD or A.D. Anno Domini (after the year 0) is often abbreviated as AD or A.D.
- Anno Domini means “In the year of our Lord,” so it precedes the date (in the year of our Lord 2018 = 2,018 years after Christ’s birth.)
- BC or B.C. can be considered “Before Christ,” so the year comes first. (1518 BC = 1518 [years] before Christ.
- 3000 BC saw the first pyramid built in Egypt.
- The first Olympiad in Greece was held in 776 BC.
- Construction on the Great Wall of China began in 214 BC.
- In AD 375, the Huns invaded Europe, beginning the end of the Great Roman Empire.
- Our calendars record that Columbus discovered America on AD October 12, 1492.
- AD July 4, 1776, was the date of the Declaration of Independence of what became the United States of America.
An alternative to those acronyms:
- CE = Common Era (AD)
- BCE = Before Common Era (BC)
- These follow the year.
- BC and BCE are growing in popularity among professional and non-professional writers.
- 3000 BCE saw the first pyramid built in Egypt.
- The first Olympiad in Greece was held in 776 BCE.
- Construction on the Great Wall of China began in 214 BCE.
- In 375 CE, the Huns invaded Europe, beginning the end of the Great Roman Empire.
- Our calendars record that Columbus discovered America on October 12, 1492 CE.
- July 4, 1776 CE, was the date of the Declaration of Independence of what became the United States of America.
With the exception of numbers that designate years (1947, 2018), using a comma makes larger numbers easier to read. For numbers higher than 999, separate them into groups of three.
In the US system, a period indicates a decimal number, a part of a whole number.
(⇓ indicates the location of the decimal point.)
- 2.085 ⇓
- 615,784.921 ⇓
- Fortunately, very few numbers (unless you’re a scientist) have this many decimal places.
- Unfortunately, there is no commonly accepted system that separates them.
Deep sigh! They changed the rules on me again!
The Chicago Manual of Style “advises” that whole numbers from zero through one hundred be spelled out with numbers from twenty-one through ninety-nine hyphenated when they are two words.
When a whole number (zero through one hundred) is followed by a larger unit (hundred, thousand, hundred thousand, etc.), both the whole number and its larger unit are written in words. (Scientists and people writing money numbers may use numbers.)
However, CMOS allows the use of numbers for large numbers not rounded off to the larger units. It is best not to start a sentence with one of those numbers, because a sentence should not begin with a number. Reword the sentence to put the number elsewhere.
- The tree sheltered three bison.
- Three bison stood under the tree.
- The tree sheltered at least twenty-three thousand ants.
- After spending all day, I counted 23,482 ants climbing the tree.
- Much better than “I counted twenty-three thousand, four hundred eighty-two ants climbing the tree.”
- Or than “Twenty-three thousand, four hundred eighty-two ants were climbing the tree.”
- CMOS also prefers omitting the “and” after “hundred.”
- Do I have to learn to rewrite my checks for one hundred forty-one dollars?
- Three tree sheltered three bison and twenty-three thousand five hundred ants (minus eighteen).
- Creativity counts for something?
Numbers giving an ordering should follow the same rules.
- “nd” and “rd” are preferred when using numbers, rather than a simple “d.”
- Others use “th” or “st.”
- Do not use superscripts for the “nd,” “rd,” or “th.”
When writing something like “to the nth degree, CMOS recommends italicizing the “n” to make it stand out.
Every rule has its exceptions, so …
To maintain consistency “in the immediate context,” if one category of rules degrees numerals, all numbers that fall in that category should be numeralized (except at the beginning of a sentence).
However, if numbers in a different category fall in the same sentence or paragraph, consistency requires using only one system for all the numbers.
- Of the 385 sheep in his flock, 76 had white faces, 29 had black faces, and the other 95 had speckled faces.
- “385” written in numbers as over one hundred.
- Other numbers also written out for consistency.
- Thirteen dogs helped corral the one hundred five sheep that escaped from the two pens.
- “Thirteen” written out because it starts the sentence.
- “One hundred five” and “two” written out for consistency.
- “and” not included after “one hundred.”
- At the end of the twentieth century, people worried about the computers not making the transition.
- Ordinal number “twentieth” written out as less than one hundred.
- “Twenty-first” would be hyphenated as is “twenty-one.”