Automatic classification of text documents has become an important research issue now days. Proper classification of text documents requires information retrieval, machine learning and Natural language processing (NLP) techniques. Our aim is to focus on important approaches to automatic text classification based on machine learning techniques viz. supervised, unsupervised and semi supervised. In this paper we present a review of various text classification approaches under machine learning

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... igm. We expect our research efforts provide useful insights on the relationships among various text classification techniques as well as sheds light on the future research trend in this domain.