Titanium is a metal — silver-white, very strong, and surprisingly light for how strong it is. That combination is the whole point of it. Because it is strong without being heavy, it goes into aeroplanes and spacecraft, where every extra kilogram costs fuel. It also resists rust and sea water very well, and the human body accepts it, so doctors use it for artificial joints, bone screws and dental implants. Sports equipment, glasses frames and expensive laptop cases use it too, partly for the strength and partly because "titanium" sounds impressive. It is a chemical element, symbol Ti, and it is usually mixed with other metals to make alloys rather than used pure. As a word it is uncountable, like water or iron: you say "made of titanium", never "a titanium". It works as a describing word in front of another noun — a titanium frame, titanium screws. Advertisers have stretched it into a loose word for "tough and premium", which is why you sometimes see it on products with very little actual titanium in them. It was named after the Titans, the giant gods, for its strength. Say it "tie-TAY-nee-um".