"Definitely" is an adverb used to express certainty or assurance about something. When someone says, "I will definitely attend the party," it means they are sure they will go. This word helps to convey confidence and removes any doubt from the statement. In everyday conversations, "definitely" can also be used to agree with someone. For example, if a friend says, "The movie was great," you might respond, "Definitely!" This shows that you share the same opinion and feel strongly about it. Using "definitely" adds emphasis and clarity to your thoughts, making your communication more effective.