topic words appear ‘together’ in the corpus. Many ways to define ‘together’ - ‘c_v’ is the best one. goodcm = CoherenceModel(model=goodLdaModel, texts=texts, dictionary=dictionary, coherence='c_v') print goodcm.get_coherence() 0.552164532134 goodcm = CoherenceModel(model=badLdaModel, texts=texts, dictionary=dictionary, coherence='c_v') print goodcm.get_coherence() 0.5269189184