Explanation:
Major Depressive Disorder is called Depression in simple language. When a person is in a low mood for a constant period of two weeks, he is said to be depressed. People who are depressed usually loose interest in enjoyable situations, they have low energy levels, they experience low self esteem, etc. Whereas Bipolar disorder is the extreme case of Depression in which the person is at a very high stage of depression called mania. It is a mental disorder. It has periods of elevated moods. We can understand this concept easily by saying that bipolar disorder is the sever form of depression.