  Liquid water is reluctant to lose hydrogen-bond coordination. Here we reveal
that it also demands contraction and reorientation of the second molecular
shell to compensate for coordination defects. Such molecular principle will be
shown to lie at the heart of the two-liquids scenario and to determine the
behavior of water in hydration and nanoconfinement. Furthermore, it allows to
define conditions for wettability (quantifying hydrophobicity and predicting
drying transitions), thus opening the possibility to elucidate the active role
of water in central fields of research.
