L1 Language-Native Language.
L2 Language-Target Language.

Supposition

1)Language as a habit and learning of a new habit.
2) The source of errors in the production in reception of  L2 is related to the native language of the speaker.
3) The reason for the mistakes in the L2 there are differences between L1 and L2 at the level of sentences,phonological system, morphological systems and syntactic systems.
4) The greater the difference between L1 and L2 the greater the difficult of learning L1 and L2.
5) The difficulty and ease of learning L2 are depended on the differences between L1 and L2.
6) Teaching of the Second Language should be center around the differences between L1 and L2.

Two Versions Of CAH

1) Strong Version or A priori Version.
2) Weak Version or A posteriori Version.