Lust is a demand of body, instinctively wild, having no discretion. All living-beings, including humans, have it but due to advancements in human civilization, lust remains suppressed or works in hiding. In civilized humans, the body demands it, mind desires it but the brain - faculty of thinking, forbids it at least in public view or knowledge. So lusty persons find excuses to be at it one way or the other.
Passion is the working of the human mind which resides part by part in every organic system of the body to regulate their functioning including passions. Every organic system has its own passion, like the visual system desires to see beautiful things, taste buds desire to find the most tasty food, etc. and most importantly for this article, the sex organs get passioned for sweet loving interaction of mating. All the passions are monitored by the brain which may impose some restrains on them.
Love is the purest of feelings for a dear one and it originates in the brain, so is the result of thoughtfulness and hence discretionary. Everyone of us wants to love some and be loved in reciprocation. Thus love flows in both directions of the relationship. This makes it the most conservative of all relationships.
The fields of lust, passion and love gets narrower in this order, meaning thereby that lust is widespread, passion is medium-spread and the love is reserved for a few, or probably the one, most beloved. Lust and passion are not necessarily reciprocal, but the love is certainly. Nobody can love a person without being loved in reverse.
A lust may get converted to a passion but not necessarily. Path from lust to love goes via mutual passions of the two for each other. A passion if positively reciprocated may get converted to a love between the two. Since there is a very thin line of demarcation between mutual passion and love, the only difference that appears is that of mutuality. Thus, a unidirectional love is passion while a bidirectional passion is love.
A passion tends to get converted to love but a pair of lover-beloved may not be passionate for each other. They may just keep on loving each other without any physical contact which is the desire of every passion.




