A photo is a short, casual way to say photograph, a picture captured by a camera. When you take a photo with your phone or a camera, you're freezing a moment in time as an image you can look at again and again.

Photos work by capturing light. When you press the button, the camera records exactly how light is bouncing off everything in front of it: your friend's smile, the birthday cake, the family dog mid-jump. A hundred years ago, taking a photo required bulky equipment and careful preparation. Today, you might take dozens of photos in a single afternoon without thinking twice about it.

People use photo in everyday conversation more often than the formal photograph. You might ask a friend to send you the photos from the field trip, or tell your parents you want to take a photo with your grandparents. The word appears in compounds too: a photo album stores printed pictures, photogenic describes someone who looks great in pictures, and a photo booth is a fun machine at parties that prints instant pictures.

While photo and pic (even more casual) mean essentially the same thing, photo sounds a bit more intentional, while pic might refer to any quick snapshot.