For example in optics there are real and virtual images.
In mathematics there are real and imaginary numbers (and many other types of numbers too).
In other subject areas - well yes, it would depend on the context.
You can't clarify 'real', it needs to be in context for it to be understood properly, because it's meaning changes depending on the other words that surround it.
Exactly the same thing happens with colour, you can't understand a single colour without any context. Same with sounds.
My assumption is that the brain works on patterns (spatial, and temporal), without enough pattern the brain hasn't got enough to go on to work out the meaning of any particular pattern with any accuracy.