Both Ruby and Python have these keywords: and, break, class, def, else, for, if, in, not, or, return, and while. The keyword def is used only for method definitions, and in is used only with for loops, not conditionals (use include? for that purpose).
Ruby has additional keywords not listed here. It does not have: assert, continue, del, elif, except, exec, finally, from, global, import, is, lambda, pass, print, raise, or try as keywords. You can use next in place of continue, and begin/rescue/ensure in place of try/except/finally. You will see exec, lambda, print, and raise as built-in methods in Ruby.