There is nothing more confusing in English grammar than the use of the comma. The comma has the ability to completely alter the meaning of a sentence and even a word.
For example, compare the following two sentences:
“What is this thing called love?”
“What is this thing called, love?”
The comma in the second sentence actually attempts to answer the question of what the thing may be. The first sentence is asking after a definition of ‘love’. A single comma changes the entire meaning of the sentence.
Commas are even more powerful yet. Compare the following two sentences:
“Joe ran as fast as he could while the house came crashing down.”
“Joe ran as fast as he could, while the house came crashing down.”
In the first sentence, ‘while’ means ‘during the same time as’. And, of the two sentences, it makes the most sense to readers. We are led to believe that Joe was trying to escape the collapsing house.
In the second sentence, the comma makes the word ‘while’ to mean ‘whereas’. The second sentence is connecting two independent clauses that make a comparison. Therefore, Joe ran fast, whereas the house came crashing down. It compares and thus contrasts their movements. Joe didn’t come crashing down, but the house did. The house didn’t run fast, but Joe did. Truthfully, the second sentence is awkward. Still, it demonstrates how a comma can so change the meaning of even a word.