Wi-Fi is a way for phones, computers and other machines to join a network — usually the internet — through radio waves in the air, with no wire going into the machine. In everyday talk it has three slightly different jobs. First, it means the technology itself: "This machine has Wi-Fi." Second, and much more often, it means one particular connection in one particular place: "The Wi-Fi here is slow", "What's the Wi-Fi password?", "Is there free Wi-Fi?" Third, people use it to mean the internet in general, which is not strictly correct but is completely normal speech: "The Wi-Fi is down" often really means the internet line outside the building has a problem, not the radio part. It is an uncountable noun, so we say "some Wi-Fi" or "the Wi-Fi", never "a Wi-Fi" or "two Wi-Fis", though the plural does show up in casual writing about hotels comparing networks. The word is neutral in tone — engineers write it in technical papers and children shout it at their parents. You will see it written Wi-Fi, WiFi, wifi and wi-fi; the company that owns the name insists on Wi-Fi, but nobody will correct you. As a verb it is rare and only very informal, meaning to give a place a Wi-Fi connection. One thing worth knowing: Wi-Fi only carries the signal the last short distance, from a box in the room to your phone. That is why your phone can show a strong Wi-Fi sign and still load nothing — the box is close and healthy, but the line from the box to the outside world is broken.