a similar process, if not identical, to the way children develop ability in their first language and which represents the subconscious activity by which they internalize the new language.

a metaphorical barrier or mental block which prevents learners from acquiring language even when appropriate input is available.

an internal device for regulating one’s language output, for editing and making alterations or corrections as they are consciously perceived.

an assumption that language acquisition occurs when one is exposed to language that is comprehensible and that contains elements that are "a little beyond" one’s current level.