Catechism number 372

Man and woman were made "for each other" - not that God left them half-made and incomplete: he created them to be a communion of persons, in which each can be "helpmate" to the other, for they are equal as persons ("bone of my bones. . .") and complementary as masculine and feminine. In marriage God unites them in such a way that, by forming "one flesh",²⁴⁵ they can transmit human life: "Be fruitful and multiply, and fill the earth."²⁴⁶ By transmitting human life to their descendants, man and woman as spouses and parents co-operate in a unique way in the Creator's work.²⁴⁷