OK, gotta respond to this. The word is "dependent." It can be both a noun and an adjective. "Dependant" is essentially a misspelling, though some dictionaries will list it as an alternative spelling. (Misused words and coinages CAN and HAVE entered the language. One example is "normalcy," a word mostly popularized by Warren Harding; that is, it was in fairly rare use in America before he uttered it in a speech in 1920.)
Enquire and inquire mean the same thing; enquire is something of a British variant. Use inquire.
As to ensure, insure, and assure, the first (ensure) basically means "to make sure," whereas "insure" means to guarantee against a loss (usually monetary). The one you don't ask about is assure, which means "to reinforce" or "to state convincingly." People often misuse that one, too.
Mukhia, I think the sign in the architect's office could have (and probably should have) read "ensure," but it's difficult to tell without the entire sentence.