Saint Valentine's Day is celebrated on February 14th. It originated from a Christian martyr named Valentine who was killed for secretly performing weddings for soldiers. The day became associated with expressing love, and people now exchange cards, gifts, and flowers with romantic partners. Common ways to express love include saying someone is a perfect match, irresistible, or holds the key to one's heart. The document also provides a sample love letter and lyrics to the song "Nothing Compares 2 U".