Abstract: The Semantic Subset Principle (SSP) predicts that learners always acquire the "subset" meaning before the "superset" meaning.The current study explores the application of SSP on language acquisition (LA).It is firstly made clear that the antithetical pair of "subset meaning" and "superset meaning" as suggested by SSP comes indeed from the typologically different ways of sentence generation, i.e.movement vs.base-generation.In terms of first language acquisition (FLA), empirical evidence alone is not enough to falsify SSP.However, the theory itself lacks explanatory and/or predicatory forces when put in the context of second language acquisition (SLA).It is proposed in this paper, based on some cross-linguistic experiments, a First Language Interpretive Priority Principle (FLIPP), stating the observed fact that the acquired meaning of a particular structure in L2 always conforms to that of the corresponding structure in L1 no matter whether such a meaning is "subset" or not in L2.Aside from general linguistic studies, FLIPP is also of great theoretical and practical significance to modern speech-language pathological studies.