that capacity of the intellect(with the aid of the body and the senses), alongside reason(with which it exists in reciprocity) which enables man to have insight and substance to the words and concepts he makes use of. not only that but to see, to perceive.
in its essentialy quality of being it is feminine.
for simplicity's sake, we may remind ourselves that we have a brain which has two hemispheres, the left hemisphere correlated with the right hand and has to do with rational thought, reason and logic.
the right hemishpehre correlated with left hand, and has to do with imagination, originality, 'irrational' feelings so on and so forth.
the understanding enables us to add new data to an idea, under a concept, words. and synthesize differnt elements from differnt ideas and concepts. it is creative.
reason enables us to analyze, critisize. but the understanding enables us to see immediately when its enough, to have temperamence and ingenuity, what time , continuous strife and practice in themselves cannot give us.
it is true, reason is that which makes us differnt from the 'animals' (or our 'lower' nature). but in a way the understanding is that which makes us different from robots.
interestinly enough, the term understanding isn't only used in psychology and philosophy, but in our daily regular and subconscious speech.
"now i see, now i understand"
("it came to me, i finally understood")
"you misunderstand, don't you see? cookies are forever. ^.^"