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.

Interjection (Wow, no way, seriously, hello)

Wow, that was amazing.

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.