The inclination of an appetite toward a good agreeing with it and adapted to it.
There is a natural love common to all creatures, whereby they naturally tend to their own proper good.
Love is sensitive or rational in so far as it arises from the apprehension of the senses only, or of human reason.
Rational love is the love of concupiscence, or of benevolence, according as its object is cherished for the good of the one loving, or of the one loved.
The love of friendship is a love of benevolence between two persons, mutually loving one another, based on a certain communication of goods.
Rational love is natural or supernatural according as it proceeds from purely natural or supernatural revealed motives.
The supernatural virtue of love (theological virtue of charity), is not acquired but infused.
It is a love of God for His own sake, and of fellow man and of self for God's sake.
True love of God and of man are inclusive of one another.
The obligation of making acts of supernatural love of God is contained in Holy Writ (Deuteronomy 6; Matthew 22; Luke 10), and urges at the dawn of reason, at the time of death, and at various times during life.
Supernatural love of God is also the principle and good of moral perfection.
The obligation of loving our fellow man binds whenever our neighbor is in need, and we are in a position to help him.
It is regulated by a certain order depending on his nearness to us by reason of relationship, friendship, country, etc., on the nature and extent of his need, and on the inconvenience, injury, or loss we undergo by helping him.
New Catholic Dictionary