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.