Second-language acquisition (SLA) designates a broad field of interdisciplinary inquiry into the process and product of instructed language learning. It addresses acquisition of languages in typical classroom settings, drawing on theories and methodologies from linguistics, psychology, sociology, or anthropology. Translations to teacher training, which includes instruction in SLA, fall within research on education. Language education concerns sequential multilingualism. Since multilinguals, particularly schoolchildren, constitute a significant proportion of referrals to specialist care, findings from both learning and teaching are relevant to communication sciences and Speech–Language clinicians, in order to understand what, how, and why learners are taught and assessed on, as well as whether and how communication in a foreign language is fostered.

SLA terminology can be vague or misleading, exemplified by each of the terms in ...