Plutarch was a Greek writer who lived around the first and second centuries AD (about 46 to 120, though the years are not certain). He is remembered for a big set of life stories, often called Plutarch's Lives: short books about famous Greek and Roman politicians and generals, often two men set side by side so you can compare how they lived and led. He cared about character — courage, pride, luck, mistake — not only battles and dates. Later readers in Europe treated him as a treasure house of those old lives. William Shakespeare, when he wrote plays set in the ancient world (Julius Caesar is the famous example), drew on Plutarch's accounts rather than inventing Rome from nothing. You say the name as a proper noun: Plutarch. It belongs in history and literature, not in everyday chat.