1 If the invitation says black tie, women should wear a floor-length, evening gown. 2  A tuxedo is mandatory if you're a man. 3  This is your chance to dress as if you were headed to the Oscars. 4  Black tie optional means that wearing a tuxedo or long evening gown is not mandatory, but guests should feel free to do so.
Ether is an organic functional group consisting of a disubstituted oxygen, or an oxygen atom bonded to 2 carbon atoms (if adjacent to a ketone, functional group is then called an ester).
This entry contributed by Leonardo Motta. Ether, or luminiferous Ether, was the hypothetical substance through which electromagnetic waves travel. It was proposed by the greek philosopher Aristotle and used by several optical theories as a way to allow propagation of light, which was believed to be impossible in empty space.