Hi Dianna!
We appreciate you bringing your question to
planDisney!
You can absolutely leave the park and return later that day if you have a
standard Walt Disney World ticket. The only thing to keep in mind is if the park reaches capacity, entry will be limited for that park. There is not a strong likelihood that this would occur, as usually, the only days that the park reaches capacity are on Christmas Day and New Year's Eve. There is no charge for returning to a park on the same day.
You will need a
Disney theme park reservation to visit any of the parks. First, make sure your tickets are linked through
My Disney Experience. Then book your reservation using the theme park reservations page. Scroll down to "Make a Park Reservation" and click on "Theme Park Tickets." The next screen will ask you to "Create Your Party," so you will select yourself and any guests you have attending with you. Click "Continue" and then select the date and park.
I hope you have a magical vacation!
Magically,
Stacy