Let’s jump straight to it, shall we?1 (No reason2 to dance around the issue.)
According to Wikipedia:3,4,5
Reason is a mental faculty found in humans, that is able to generate conclusions from assumptions or premises. In other words, it is amongst other things the means by which rational beings propose (specific) reasons, or explanations of cause and effect. [emphasis in the original]6
The crucial point to take away from this is that reason, in the abstract sense, is something that is usually associated with sentience in general and humanity in particular.7 Reason is, many would say, that thing which separates men from beasts.8 It is fairly reasonable to assert that reason is requisite to defining human behavior, and by contrast to assert that the abandonment of reason is the abandonment of humanity.9
The definition above defines reason in terms of reasons, which are logical rather than cognitive. It’s certainly not a coincidence that the two concepts use the same word, since the former is strongly dependent on the latter; in a sense, reasons are the mechanisms we invoke to utilize our capacity to reason.10
