TGIF is short for "Thank God It's Friday." People say it — or write it — when the working week is finally ending and two free days are coming. It carries a feeling more than a fact: relief, tiredness, and a small happiness that the hard part is over. You can say the four letters out loud, tee-gee-eye-eff, or write them in a message. It is casual and friendly, so it belongs with friends, with people you work beside every day, and in chat messages. It would look strange in a formal letter or a report. Notice that the person saying it is usually not thinking about God at all; the phrase became a fixed set of sounds long ago, and even people with no religion say it easily. Some people also use it as a name for a thing, not just a feeling — a TGIF drink after work, a TGIF party. And there is a restaurant chain called T.G.I. Friday's, which took its name from the phrase, so in some places the letters make people think of food first. One more honest point: it only works if your rest days really are Saturday and Sunday. People who work weekends often say it as a joke, or with a small complaint attached, because for them Friday is just another day.

感謝老天，終於星期五了（口語常說「終於星期五了」「週末終於到了」）