An ax is a sharp tool for cutting wood. When you split logs, you hold the handle, swing the ax into the air, and let the blade fall on the wood.
Most axes have a long wooden handle connected to a blade made of sharpened steel. An ax is a useful tool to own if you have a wood stove or are building a campfire. You can also spell the word with an e at the end: axe. As a verb, to ax means to fire someone from a job: "He was late so many times that I finally had to ax him."