Zoom Webinars

Zoom says, "over 100" participants for a Webinar, but what if less than 100 join, can you still use the webinar functions?  I have Zoom Pro now, but an upcoming meeting has filled up and I want to allow more people in so I'm considering an upgrade.  However, in the future, I may only have 50-60 people in a webinar.  Can I put on a "webinar" with less than 100 or would that be considered a "meeting"?