These two tenses both express actions and states in the past. However, the imparfait should be used in cases of repetitive situations, a description or an action without a limited time frame. For instance, "everyday I woke up at dawn" should be translated using the imparfait. On the other hand, the passé simple is used in cases of a sudden or unexpected event, or to express a finished action. Quite often these two tenses are combined within a sentence to add impact to an idea. For instance, in the sentence "She was walking in the park when she saw a sparrow.", the fact of seeing the sparrow is emphasized by the previous use of the imparfait.