If you are able to check out the lenses in a shop, it would be worth taking your camera with you and seeing if the lenses on offer do match up, and if the selected focal length is a suitable choice. Would you want to have a 50mm prime lens as well as a 18-70mm zoom that covers this focal length? I admit that I have a 50mm and a 35-105 mm zoom, for my film camera, but only because the 50mm has a large f1,4 aperture allowing use in lower light levels, which may not be so important with a digital camera due to the greater sensitivity of the pickup device.
I have a Canon film camera and whilst the Canon lens fitting was quite different to any other camera, there were some non Canon manufactured lenses which had the unique Canon fittings, so could be used with a Canon camera. The same lens manufacturer also made them with alternative fittings for other makes of camera. The display of alternative lenses always specified what camera they were intended to fit.
IF you are shopping from catalogue or advertisements in a photographic magazine, the generic lenses would specify what camera they are intended to fit. It is usually possible to fit a manual focus lens to a camera that normally takes an autofocus lens, if the camera is an SLR, and you have a clear viewfinder image. Again worth trying that out before you buy it, in order to see if your manual focusing is accurate. These manual and generic lenses are often cheaper than 'own make', but do try them out first if you can.