Grammar: How to use commas
Introductory phrase
Before the bell rings, students drink from the water fountain.
To separate list items
I like chicken, beef, and bacon.
Join two related sentences (needs a transition like: ", but" or ", however"
I ran up the hill, but he fell down it.
When two adjectives describe the same noun
It was a difficult, stubborn animal.
Nonrestrictive phrases or clauses
Phrase: The students, trying to pass the test, studied long into the night. Clause: The gym, which was made in 2002, is now the center of the athletic complex.
Contrasting phrases within sentence
Playing soccer, not volleyball, requires a lot of running.
A phrase normally within parentheses
The boy, as slow as ever, marched into class.
Why are commas important? Here are some examples:
The example below demonstrates just how powerful punctuation can be (no doubt the second option is correct): A woman, without her man, is nothing. A woman: without her, man is nothing. Note the change in meaning when commas are used with restrictive and non-restrictive clauses: "I want to thank my parents, John and Lisa" (thanking 2 people) vs. "I want to thank my parents, John, and Lisa (thanking parents [2 people] and John and Lisa) CORRECT GRAMMAR CAN SAVE A PERSON'S LIFE! Let's eat, Grandpa! Let's eat Grandpa!
Around phrases or words adding more detail to a previous statement or noun (explaining)
We worked, standing in the hot field, all day.
Interjection (Wow, no way, seriously, hello)
Wow, that was amazing.