We show that the main features of the pattern of fermion masses and mixing can be expressed in terms of simple relations among weak-basis invariants. In the quark sector, we identify the weak-basis invariants which signal the observed alignment of the up and down quark mass matrices in flavour space. In the lepton sector, we indicate how a set of conditions on weak-basis invariants can lead to an approximate tribimaximal lepton mixing matrix. We also show the usefulness of these invariants in the study of specific ans��tze for the flavour structure of fermion mass matrices.

16 pages, 1 figure