What do you consider a “classic” work of literature

Earlier today, I found myself in an interesting conversation about what books qualify as classics. I mentioned that it's quite a subjective topic, but I rattled off a few titles that immediately came to mind: Pride and Prejudice, Black Beauty, To Kill a Mockingbird, The Great Gatsby, Moby-Dick , The Catcher in the Rye, Great Expectations, The Age of Reason, Little Women, and The Secret Garden.

We then debated The Secret Garden; while often labeled a children’s novel, I argued that its profound message and impact justify its classic status. On the other hand, books like Black Beauty, Moby-Dick, Little Women, and To Kill a Mockingbird seem to be clear-cut classics, both for fitting the traditional definition and for their lasting societal impact.

What really makes a book a classic, in your view? Does it have to change the way we see the world, or is it about the timelessness of its themes and characters?

This discussion made me reflect on how these books have influenced our perspectives and remain relevant through the ages. Any thoughts on what you'd add or how you define a classic?