What is a GCF?

The abbreviation "GCF" means Greatest Common Factor. A GCF is the highest number that can be multiplied that two numbers have in common. An example is that the number 4 is the GCF of 8 and 12. That means when you are comparing the numbers 8 and 12, the highest number that they share that can be multiplied to equal either 8 or 12, is 4.