  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\"atze for the
flavour structure of fermion mass matrices.
