can i replace my rims 622x19 hybrid for a 622x17? i have a bike my rear wheel was stolen here in DC. the original was a 622x19. i have one which is 622x17 my question. is that ok ans safety to use it on ky bike? 
thank you.
You should be perfectly fine, the 622 is the ERD [effective rim diameter] in mm. The other number is the inner width of the rim. What this effects is the range of tire the rim will hold. So your rear wheel will be slightly thinner, which is kinda strange but not that big of a deal. You can probably fit a 1.95" (700x50) tire on there without any issues but i would not try and go any wider than that. If your using 700x35 or something similar you should be just fine. 

Make sure to check the axle spacing though, you can measure the axle of the replacement you have and then measure the rear dropouts. If its a steel frame and they do not match you should be able to space the frame a little with no issues. If its an aluminum frame make sure the wheel is the correct axle length. You can't space aluminum.

So yes! You can use that size rim with no issues assuming it is the same axle spacing. As always if your change to a larger tire size make sure your frame has clearance but it sounds like what your doing is pretty straight forward.