| Term | Definition |
| the monitor hypothesis | Part of the learned system. Alters the output of the acquired system.The monitor is intended to link the acquired and learned systems in a situation of language use. It acts as the 'editor.' |
| conditions of the monitor | time, focus on form, and know the rule |
| natural order hypothesis | Elements of language (or language rules) are acquired in a predictable order. the order is the same regardless of whether or not instruction is involved. A result of the acquired system, without interference from the learned system.The natural order was determined as a result of the morpheme order studies. |
| affective filter hypothesis | Includes motivation, ego permeability, ambiguity tolerance, attitude, introversion/extroversion, self-confidence, and anxiety. If the filter is up, input is prevented from passing through and no acquisition can take place (Input will not reach language acquisition device).The aff. filter is responsible for individual variation in SLA. Child lang. acquisition does not have an affective filter. |
| output filter | ability, willingness to produce output. (e.g., speaking in front of a group, may not be able to perform) |