hi! not discouraging the mathematics (or philosophy) experts from weighing in here, but you can get a start in these previous posts. The tl;dr is that while they had no numeral to represent nothing, they did have the concept of nothing

• How did mathematics work before the introduction of the number zero?

• There is no Roman numeral for the number zero. How would a Roman mathematician answer the equation X minus X or V minus V? What about V minus X?

.. and, for any other readers who may be interested in the topic of zero in general, check out this recent post, which includes links to several more

• Who were the first people to realize zero and negative numbers?

as always, if you have follow-up questions on old locked posts, ask them here & include the relevant user's username so they'll get an auto-notification