According to one embodiment, a dialog system includes a processor. When a first sentence including one or more words is input by a user, the processor sets at least a part of the one or more words as a first query keyword. The processor selects, from a question-answer table including question-answer pairs, one or more of the question-answer pairs including the first query keyword. Each question-answer pair includes a question and an answer to the question. When a number of the selected question-answer pairs is 1, the processor outputs a first response indicating the answer. When the number is not less than a first threshold, the processor outputs a second response including first and second question keywords. The first question keyword is extracted from question keywords included in one of the pairs. The second question keyword is extracted from other question keywords included in another one of the pairs.