Monogamy
Around the world people have different rules for their relationships - rules often dictated by culture and religion. In many societies the most important of these is sexual fidelity - true love and monogamy are expected to go hand in hand - but why should love mean forsaking all others? And what happens to relationships when monogamy is cast adrift?
(Image of couples kissing and celebrating the eve of Valentine's Day. Credit: Getty Images)
