Term
Transition Zone
Also called: Midcourt
The area between the baseline and the kitchen line, which you pass through on your way up to the net.
The area between the baseline and the non-volley zone line (kitchen line) (USA Pickleball). Here you are likely to get hard balls hit at your feet, so it is said that you should pass through quickly and move up to the kitchen line (USA Pickleball).
How to read the sources: numbers like (8.F.4) are rulebook sections, and links are outside sources. An "Author's note" is the author's personal experience, not an official rule.