Don's Home Reference | Spell Checkers Some Grammar and Spelling Rules

Some common rules:
Things I commonly get caught on.

Clauses - A group of words that have a subject (noun or pronoun) and predicate (verb).
Sometimes the subject is understood. "Call the plumber, please." ("You" is understood subject)

Phrase - a group of words does not have a subject and predicate.

Independent Clause - Can stand alone and make a complete thought.

Dependent Clause - A clause which does not express a complete thought.
Requires an independent clause to make a complete sentence.
e.g. "when I finish my work."
See more at:
What Are Basic English Grammar Rules?
Elements of Sentence Construction

Use a comma between independent clause, e.g.
It's cold outside, and I can't find my coat.
I can't find my coat has a subject and verb, so is independent.

Don't use a comma between dependent clauses, e.g.
Sam tossed the ball and watched the dog chase it .

There is a debate about when to use Oxford (or Serial) commas, the final comma in a list of things. According to grammarly both of the following are correct.
The dog is young, well trained, and good natured.
The dog is young, well trained and good natured. (no oxford comma).

A rule of thumb is to check whether the word in question needs a comma before it. If it does, use which; if it doesn't, use that.

The Oxford University style guide, however, states: "Note that in British English, the word which is often used interchangeably with the restrictive that".

1. Use a comma before any coordinating conjunction (and, but, for, or, nor, so, yet) that links two independent clauses.
2. Use commas to separate items in a series.
3. Use a comma after a dependent clause that starts a sentence.
4. Use commas to offset appositives from the rest of the sentence.
   An appositive is a word or phrase that refers to the same thing as another noun in the same sentence.
   If you could remove the appositive without changing the meaning of the sentence, it is said to be nonessential and should be set off with commas. If the appositive is necessary, it's said to be essential and it should not be set off with commas.
   Essential - "Edgar Allan Poe's poem The Raven is a classic."
   Nonessential - "My mother, Angela, is a wonderful cook.
5. Use a comma after introductory adverbs.
6. Use a comma when attributing quotes.
   If attribution comes before the quote, place the comma outside the quotations marks.
   If attribution comes after the quote, put the comma inside the quotation marks. "I saw a duck," said the runner.
7. Use a comma to separate each element in an address. Also use a comma after a city-state combination within a sentence.
8. Also use a comma to separate the elements in a full date (weekday, month and day, and year). Also separate a combination of those elements from the rest of the sentence with commas.
9. Use a comma when the first word of the sentence is freestanding "yes" or "no."
10. Use a comma when directly addressing someone or something in a sentence.
    e.g. My editor often asks, "Christina, is that article up yet?"
11. Use a comma between two adjectives that modify the same noun.
    e.g. "I saw the big, mean duck when I went running."
12. Use a comma to offset negation in a sentence.
    For example: "I saw a duck, not a baby seal, when I went running."
13. Use commas before every sequence of three numbers when writing a number larger than 999. (Two exceptions are writing years and house numbers.)

• Most Words in Titles (This is a title)
• First Word of a Sentence
    Don't Capitalize After a Colon (Usually)
• Capitalize Names and Other Proper Nouns - and adjectives derived from proper nouns.
  - Freud, a Freudian slip
  - Some words originally derived from proper nouns have taken on a life, and authority, of their own and no longer require capitalization.
      herculean effort
  - Names: Rin Tin Tin was a German Shepherd who was a movie star.
  - Capitalize words like mom and grandpa when they are used as a form of address.
      Just wait until Mom sees this!
      My mom is not going to like this.
  - Brand Names, Companies
  - Organizations: Department of Agriculture, Sierra Club
    Note: Many authorities do not capitalize federal or state unless it is part of the official title.
  - Cities, Countries, Nationalities, Races, and Languages are Proper Nouns
      (Note: white and black in reference to race are lowercase)
  - Places - Mount Everest, Street Names
  - Directions e.g. southwest are not capitalized or hyphenated - Days, Months, and Holidays are proper nouns. But Not Seasons
  - Capitalize the Bible (but not biblical, heaven, hell, the devil)
  - Capitalize church when it refers to a specific church denomination as a whole or a specific local church: Roman Catholic Church, The Protestant Christian Church.
  - Don't capatilize when if refers to a building, group of Christians. "Our church was built in 1833."
• Capitalize the First Word of a Quote (Sometimes)
• Capitalize Time Periods and Events (Sometimes)
    World War I, Middle Ages,
    Not centuries - seventeenth century
  

Surface measurements.
Square foot - The most common of these abbreviations is sq. ft.
ft² is preferred but sq. ft or sqft or SF are also used.
The html code for superscript 2 is ² e.g. "ft²" for ft²

• affect/effect

  Use affect to indicate influence: The medicine did not affect her the way the doctor had hoped.

  Use effect as a noun: The new medicine had negative side effects.

• complement/compliment

  Use complement when referring to something that enhances or completes: The cranberry sauce is a perfect complement to the turkey dinner.

  Use compliment as an expression of praise: I was pleased to have received so many compliments on my new dress and shoes today.

• lie/lay

  Use lie to indicate the act of reclining: I am tired just watching the dog lie in the warm sunlight.

  Use lay to indicate the placement of something: Please lay the paper on the table.
  Lay is a transitive verb, which means it always needs an object!

• capital/capitol

  Use capital when referring to a city, a wealth or resources, or an uppercase letter: The capital of Maryland is the gorgeous city of Annapolis.

  Use capitol when referring to a building where lawmakers meet: The capitol has undergone extensive renovations this year.

• principle/principal

  Use principle as a noun meaning a basic truth or law: Many important life principles are learned in kindergarten.

  Use principal as a noun meaning the head of a school or organization, or a sum of money