Definitely means without any doubt or uncertainty. When you say something will definitely happen, you're expressing complete confidence that it will. If your friend asks whether you're coming to their birthday party and you answer “definitely,” you're making it clear there's no chance you'll miss it.

The word carries a sense of firmness and certainty. Compare “I'll probably be there” (maybe yes, maybe no) with “I'll definitely be there” (count on it). When a teacher says the test will definitely cover Chapter 5, students know for certain they need to study that material.

People sometimes confuse the spelling, writing “definately” instead of definitely. Something definite has clear boundaries and no vagueness. When you definitely know the answer to a question, you're not guessing or hoping you're right.

The word strengthens your statements and removes wiggle room. When you commit to something definitely, you're giving your word with confidence. It's a powerful way to show you mean exactly what you say.