A GIF is a kind of computer file for pictures, made so they could travel easily on the internet. The letters stand for Graphics Interchange Format. The old use was a still picture with few colours, so the file stayed small. The use students meet now is the short looping moving picture: a cat dancing, a face saying no, the same few seconds playing again and again, usually with no sound. People drop GIFs into chat the way they drop stickers. Though actually, a lot of the “GIFs” on your phone today are not true GIF files — apps often use a video format because it is smaller and looks cleaner — but everyone still calls them GIFs. There is a long, slightly silly fight about the sound: the man who made the format said “jif,” like the peanut butter; most people say a hard G, like “gift” without the t. Both are used. Informal internet English; you can even stretch it into a verb, “to GIF” a moment, meaning to turn it into one of those loops.