Tribimaximal mixing is a specific postulated form for the Pontecorvo–Maki–Nakagawa–Sakata (PMNS) lepton mixing matrix U. Tribimaximal mixing is defined by a particular choice of the matrix of moduli-squared of the elements of the PMNS matrix as follows: This mixing is presently excluded by experiment at the level of 5σ. The above prediction has been falsified experimentally, because θ13 was found to be nontrivial, θ13 =8.5°.