It's not that simple. Some signs may be different, some may not. A deaf person across town from me may use a different sign to ask to use a washroom. He may sign "toilet" while I sign "restroom."
I felt the same frustration you feel when I was learning German. Spelling was wonderful, but all the many genative and dative cases in grammar nearly drove me crazy, because English rarely uses them. I wanted it to be simple, damn it!
Languages really resist neat pigeon holes.
