What is an Ntuple

nTuple is a colloquial term for ROOT TTree objects, which are designed to store an array of arbitrary (well, almost) collections of C++ objects (abstractly, tuples) in a way that allows fast (de)serialization to disk. The history of nTuple is interesting: one can still see the legacy TNtuple, which was a class designed to be more familiar to users of PAW, the predecessor to ROOT. To see how much worse your life could be, check out these NTUPLEs.