I. Introduction II. Bilinguality and Bilingualism III. Age Factor in the Development of Bilinguality a) Childhood Bilinguality b) Adolescent Bilinguality & Adult Bilinguality IV. Age Factor and Second Language Learning V. Major Critical (Sensitive) Period Hypotheses on Second Language Learning a) The Younger the Better b) The Older the Better c) The Younger the Better at Acquiring Accent Interpersonal Communicative Skills d) The Younger the Better in the Long run VI. Conclusion REFERENCES Abstract