This essay examines language simplification for second language learners as a linguistic and a pedagogic phenomenon, posing questions for further study by considering past research. It discusses linguistic simplification (LS) in relation to the development of artificial languages, such as Esperanto, "pidgin" languages, Basic English, motherese, teacher-talk, and foreigner talk. LS is also considered in relation to first language acquisition. Pedagogic simplification (PS) is discussed in light of the development of frequency-based word lists, graded readers, criticism of simplified learner materials, modification rather than simplification of learner materials, and the schema theory of teaching and learning. (MDM)