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).
Ether, any of a class of organic compounds characterized by an oxygen atom bonded to two alkyl or aryl groups. Ethers are similar in structure to alcohols, and both ethers and alcohols are similar in structure to water. In an alcohol one hydrogen atom of a water molecule is replaced by an alkyl group, whereas in an ether both hydrogen atoms are replaced by alkyl or aryl groups.