New Game Plus
Also said as NG+, Second playthrough
After finishing the game, you start over and keep something from the first run, such as your levels, items or knowledge.
It asks very little of you and doubles the life of everything you have built. It works best when the second run reveals new things, and doesn't just inflate the enemies' numbers.
Say it
“Add New Game Plus: keep levels and the cellar key. The key opens a door that sits locked through the first run, and characters who remember you get a new line.”
Where you’ve seen it
Chrono Trigger gave the option its name in 1995, and you need it to see most of its endings. Nier: Automata goes further: its later playthroughs show you the same events from another character's side.
Not to be confused with multiple endings
New Game Plus changes how you begin. Multiple endings change how you finish.