Krashen’s widely accepted theory is built upon Five hypotheses:
1) The Acquisition-Learning Hypothesis in which he differentiates between Language Acquisition and Language Learning.
2) The Natural Order Hypothesis in which he assumes that grammatical structures are acquired in a predictable order.
3) The Monitor Hypothesis in which he states that conscious learning has a very limited function in adult second language performance.
4) The Input Hypothesis in which he states that we acquire (not learn) language by understanding input that is a little beyond our current level of competence.
5) The Affective Filter Hypothesis in which he states that attitudinal variables relating to success in second language acquisition generally relate directly to acquisition but not necessarily to learning.
