Pertinent means directly related to what matters right now. When your teacher asks a question about the American Revolution and you bring up something about ancient Rome, that's not pertinent to the discussion. But if you mention the Boston Tea Party, that's perfectly pertinent because it connects directly to the topic at hand.

Information becomes pertinent when it actually helps answer the question or solve the problem you're facing. If you're writing a report about whales, facts about dolphins might be interesting, but they're not pertinent unless you're comparing the two animals. If you're trying to figure out why your science experiment failed, the temperature of the room might be pertinent, but what you ate for breakfast probably isn't.

The word suggests a kind of usefulness: pertinent details are the ones worth paying attention to because they matter to your specific situation. When a detective investigates a crime, she focuses on pertinent clues that actually help solve the case, not every random fact about the neighborhood. In a courtroom, lawyers can object if someone brings up information that isn't pertinent to the case being tried.

Learning to recognize what's pertinent is a valuable skill. It means you can sort through lots of information and identify what actually matters for the task you're working on right now.