What is valentine? How to use in English

The origin of the word "Valentine" dates back to the ancient Roman Catholic Church. According to Christian tradition, Saint Valentine was a priest who lived in Rome during the 3rd century AD. Emperor Claudius II had outlawed marriage for young men because he believed that single men made better soldiers. Saint Valentine defied the emperor's decree and continued to perform marriages in secret, and as a result, was put to death on February 14th. During his imprisonment, Saint Valentine healed the daughter of his jailer and before his execution, he wrote a letter to her signing it "From your Valentine," which became a familiar phrase associated with the saint. Over time, the name Valentine became synonymous with love, romance, and expressions of affection, leading to the tradition of exchanging Valentine's Day cards and gifts on February 14th.