Answer: is understood under passion a not reflexive impulse linked to intuitive, immediate reaction, that has developped itself in time towards the understanding of a blind attachment to another inside of what may be still considered boundaries of love, and later, this understanding has broadened itself to refer itself to all sorts of activities mind attaches itself to without too much of a thought: a passion for cinema, for example.
Reason, on the other hand, a complexe notion of multiple interpretation (going from the Greek nous, more spiritual, to the Lation ratio, that understands under this term the ability of sharing in equal parts), seems to stabilize itself around an understanding attaching it to an intellectual activity allowing the putting frein to impulses and/or passion by the deliberate submission of the ‘I’ to a certain number of laws that may include the taking into consideration of social rules in image, being this ability at the origin of ‘reason’, that is to say, intellectual activity or thought as taking its source in it. Shifting often between a notion reminding more to common sense (as if what everyone does were in itself a mean to control instinct, passion and even unjustice, for example), Rousseau, and the submission of intuition to a formal pattern in law, Kant, it is one of the philosophical concepts with less determination that can be found.
But, having all this in mind, it would be possible to say that in general, reason is considered a regulator for passion, linked to intellectual activity, and possible location of the conscious ‘I’ in its relation to intuitive impulses. Thus, the difference between both would be that one is an activity or ability that has the ‘I’ attached to itself, while the other is a mass of forces the ‘I’ has to deal with whose origin can not be said intellectual.
« Los sueños de la razón producen monstruos. » (Goya) The dreams of reason produce monsters.
It seems as if it may be said, on the other hand, that the fact of not making use of reason to regulate intuitive impulses and make of it a ‘finality in itself’, may be at the origin of irrationality in this that the ability is used for not adequate purposes. In this case, you don’t talk about a difference between both, but of a … divorce.