The ideas of singular term and of general term in predicative position play a central part in Quine's theory of canonical notation. This chapter examines two attempts to explain these ideas. It argues that they rest upon certain other notions whose role as foundations is not clearly acknowledged in Quine's explanations. The fundamental distinction can, in fact, be yet more narrowly specified. Singular terms are what yield truth-value gaps when they fail in their role. Quine distinguishes between definite and indefinite singular terms. Quine mentions another way, which he also thinks unsatisfactory, of trying to bring out the difference between definite singular terms and general terms in predicative position. The position occupied by a definite singular term of any kind may be coherently yielded to a kind of term which does not characteristically have the identifying function of a definite singular term, and which is called an indefinite singular term.