a good definition of consciousness I was having a conversation with a non buddhist about consciousness I was struggling to define some key aspects and it kind of led into not self,  but I was looking for a concise simple definition.
Technically, consciousness (viññāṇa) is that aspect of the mind that is aware; it is the qualia of modern Western philosophy.
Colloquially, it is used to refer to the entire mental ensemble that includes sensation (vedanā), recognition (saññā), processing (saṅkhāra), and awareness (viññāṇa). This is because the other three aggregates are always accompanied by awareness. Just as water has colour, temperature, etc., so too, consciousness has sensation and other mental concomitants.
Doctrinally, it is a cornerstone of Buddhist philosophy, which takes an experiential paradigm as the basis of reality (as opposed to the temporospatial paradigm of modern science). Each conscious qualia constitutes an atomic entity in the complex matrix of multi-perceptional reality.

cittena nīyati loko, cittena parikassati.
cittassa ekadhammassa, sabbeva vasamanvagūti.
By the mind the world is led, by the mind is it carried away.
Of the mind, the one thing, all indeed go according to its power.
-- SN 1.62