Use a comma between two or more adjectives that describe the same noun if they could be reversed and still make sense.
Example:
* "The big, red ball" - You can say "the red, big ball" and it still makes sense.
Important Notes:
* Not all adjectives need commas. If the adjectives are closely related (like "small, blue car" or "comfortable, cozy chair"), they usually don't need a comma.
* Consider the flow. Even if the adjectives could technically be reversed, sometimes a comma makes the sentence sound awkward. In this case, you can omit the comma.
Here's a simple way to test if you need a comma:
1. Can you put the word "and" between the adjectives? If you can, then you likely need a comma.
2. Does the order of the adjectives change the meaning? If not, you likely need a comma.
Examples:
* "The beautiful, old house" - You can say "the old, beautiful house."
* "The sharp, dangerous knife" - You can say "the dangerous, sharp knife."
* "A tiny, yellow bird" - You can say "a yellow, tiny bird."
However:
* "A bright yellow bird" - "Bright" modifies "yellow," so they're closely related and a comma isn't needed.
* "A comfortable, cozy armchair" - While you could reverse these, the comma sounds awkward here.
Overall, the best way to ensure correct comma usage is to think about the meaning and flow of the sentence.