This paper starts from the assumption that "practice-driven inquiry" should constitute the fundamental focus of Translation Studies in order to encourage translators/translation teachers to reassess the variety of approaches and techniques that translators employ in actual practice. Thus, TT expansion is explored as one of such inquiry topics. The first part reviews different theoretical accounts of such phenomenon in order to establish a consensus as to the starting point of further research: TT expansion occurs as a result of the translator's decision to secure information equivalence between ST and TT. The underlying assumption is the existence of the gap between ST and TT regarding the extent of "retrievable knowledge" as well as identifies the different layers where the phenomenon is observable. The second part establishes the degree of shared knowledge as a variable that determines the degree of translator intervention and the consequent TT expansion. The third part acknowledges the need to consider "reader status" in relation to any attempt to determine the degree of TT expansion and sufficiency of translation. The conclusion acknowledges a need to introduce a new text typology that uses the degree of shared knowledge and presupposed reader design as two variables.
