Lastly means finally or at the end of a series of things. When you're explaining several points and reach the last one, you might say “lastly” to signal you're wrapping up.

A teacher might say, “First, we'll review multiplication. Second, we'll practice division. Lastly, we'll take a quiz.” That lastly tells students the quiz is the final item on today's agenda.

The word works similarly to finally or in conclusion, but it specifically emphasizes sequence and order. You're marking the last item in a list or the final step in a process. A recipe might instruct: “Mix the dry ingredients, add the wet ingredients, and lastly, fold in the chocolate chips.” That lastly makes clear which step comes at the very end.

Writers often use lastly in persuasive essays or speeches when presenting multiple arguments. It helps readers follow along and signals that the conclusion is near.