Learning a second language (L2) is not merely mastering an additional linguistic system, but rather learning a new way of conceptualizing the world. Grammatical development does not always align simultaneously with conceptual development in L2. That explains why L2 learners may produce sentences that are grammatically correct, but pragmatically inappropriate. Research needs to address conceptual fluency which consists of, but not exclusively, formulaic competence and metaphorical competence. There should be a shift from a focus on isolated grammar and formal knowledge to the changes that first-language-governed conceptual base undergoes in the process of second language acquisition. A competent second-language learner is expected to use the target language in ways that native speakers use it. Conceptual fluency has substantial pedagogical implications in L2 acquisition.