Righto, I guess it depends on whether you are talking about a lower-priced interpretation of a trend or designer item, vs. something intended to make one think you have the "real thing" and possibly violating production rights, or even , can you always tell a difference?
So, are Zara runway-inspired items knock-offs?
I also try to evaluate quality and fit and avoid (or try to) buying items that are poor renditions of a trend, when a better-made, classic item would be, well, better. So I don't mean, if you can't get the real thing, don't bother, but more that , companies seem more likely to take shortcuts if they're trying to emulate something very specific but rapidly and on a tight budget, vs. able to work with the materials, supplier, manufacturer and so on to get a good product for the cost.
So, for example, with the mixed-media trend there have been a lot of cobbled-together, plasticky-looking items vs. others that have a nicer vibe even if faux leather is used.
Being not very brand-savvy, as in not recognizing iconic handbags and such, I think I am still at great risk of buying something that is "new" to me but is actually a knock-off of sorts from something either recent or from several years ago--not intending at all to be buying whatever it is supposed to be knocking off, but just liking the design or color or something. Or being semi-intentional, as in, I may look at style photos for inspiration but don't pay attention to who makes what.
I kind of hate that that could happen--me sporting my good-deal whatever, and not even being IRONIC, and someone judging me for it--but you know, life's just too short for that!