The effective causes on second language in history science

The language learning is the most important duty for all students who want to continue their educations in a foreign country; I think this is the most interesting question for every language learner which how many causes are there to effect on second language learning. In this article we try to show the different causes which effect on second language learning. It is clear that the effective causes on second language learning are more complicated than we believe; the complication depends on the language system complicated composition, while the language is not a simple and plain structure so, learning of language might be caused by different components even in opposite manner. Talking about the language on the other word is talking about humankind; as we know discussion on the humankind as a topic is not so easy it relates to many parts of knowledge like psychology, sociology, history, anatomy, etc. therefore, discuss about the causes which effect on the language learning process needs a comprehensive study that until we can conclude what causes effect on language learning. We will discuss about the following subjects which almost cover all of the mentioned points: The age of language learner; Psychological characteristics of language learner; Causes of society, cultural environment of language learner; Characteristics of native language of language learner. Key words: second language, causes, effect, foreign language.