where, wherefore (see usage note at the current entry)
Where … at (Where was he at?) and where … to (Where is this leading to?) are often criticized as redundant because neither at nor to adds anything to the meaning of where, and sentences like the preceding ones are perfectly clear and standard without the final at or to. This criticism does not apply to where … from, which is fully standard: Where does the money come from? The constructions where … at and where … to occur in the speech of educated people but are rare in formal speech and edited writing.
in, at, or to what place, point, or position?: where are you going?
(used in indirect questions): I don't know where they are
in, at, or to which (place): the hotel where we spent our honeymoon
(subordinating) in the place at which: where we live it's always raining
(usually pl) a question as to the position, direction, or destination of something
It was formerly considered incorrect to use where as a substitute for in which after a noun which did not refer to a place or position, but this use has now become acceptable: we now have a situation where/in which no further action is needed
Old English hwǣr, hwār(a); related to Old Frisian hwēr, Old Saxon, Old High German hwār, Old Norse, Gothic hvar
Old English hwær, hwar, from Proto-Germanic *khwar (cf. Old Saxon hwar, Old Norse hvar, Old Frisian hwer, Middle Dutch waer, Old High German hwar, German wo, Gothic hvar "where"), from PIE interrogative base *qwo- (see who).