An ELT Glossary : The Monitor Model

A theory of second language acquisition proposed by Krashen in his work in the 70s and 80s, particularly in his book Principles and practice in second language acquisition (1982).  
The model consists of five hypotheses : 

1. The Acquisition-Learning Hypothesis

2. The Monitor Hypothesis

3. The Natural Order Hypothesis

4. The Input Hypothesis

5. The Affective Filter Hypothesis.


Further reading : Baker, C. and Prys Jones, S. Encyclopedia of Bilingualism and Second Language Acquisition