A morphism α is (strongly) unambiguous with respect to a word α if there is no
other morphism τ that maps α to the same image as σ. Moreover, α is said to be
weakly unambiguous with respect to a word α if σ is the only nonerasing morphism......
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.