According to the Abhinaya Darpanam, the Sangitaratnakara and other medieval treatises, dance is divided into three distinct categories, that is, natya, nritya and nritta.
Natya corresponds to drama. Natya means dramatic representation or drama with speech, music and dancing. According to Abhinaya Darpanam,
‘Naatyam tannaatakam chava pujyam purvakathaayutam‘,
that is Natya or Nataka which has some traditional story for its theme is an adorable (art).
Nritya corresponds to the mime performed to the song. That is in other words, it is the Interpretative dance. The vaachikaabhinaya of natya where the actors themselves use speech, is replaced by the music and song which accompanies dance.
According to Abhinaya Darpanam,
‘Rasabhaavavyanjanaadiyuktam nruttamitiryate, etannnrutyam mahaaraajsabhaayaam kalpayet sadaa‘,
that is, that dance which relates to Sentiment (rasa) and Psychological Staes (bhaava) is called nritya.
Nritta corresponds to pure dance steps performed rhythmically. Here the movements of the body do not convey any mood or meaning and its purpose is just creating beauty by making various patterns, lines in space and time.
According to Abhinaya Darpanam, ‘Bhaavabhinayaheenam tu nrittmityabhdheeyate‘,
that is, that dance which does not relate to any Psychological State (bhaava) is called nritta.