Hasya Rasa is an integral part of the Natyashastra
. Laughter is the Sthayi Bhava or the dominant emotion in Hasya rasa. The determinants or Vibhavas of Hasya rasa are Vikrtavesa (Unseemly dress), Vikrtalankara (misplaced ornaments), Dharstya (Impudance), Laulya (covetousness), Kalaha (quarrel), Asatpracapa (near-obscene utterance), Vyanga Darsana (displaying deformed limbs), Dosoda Harana (Pointing out the faults of others) and other related things. In the dramatic performance it is displayed through the Anubhavas or consequents like biting the lips, throbbing of the nose and the cheek, opening the eyes wide, contracting the eyes, perspiration, colour of the face, holding the sides and others.
The Vyabhicari Bhavas or the Transitory States of Hasya Rasa are lethargy, dissimulation, drowsiness, sleeplessness, dreaming, waking up, envy and other things.
Hasya is of two kinds, Atmastha or self-based, Parastha or based in others. When the actor laughs to himself it is called Atmastha when he makes another laugh it is called Parastha. The display of oddly placed ornaments, unseemly behaviour, irrelevant words, faulty dress, strange movements of the limb etc. make people laugh so this Rasa is called Hasya.
This Rasa is most common to women characters and persons of the mean order. It has six distinct varieties which are Smita (gentle smile), Hasita (slight laughter), Vihasita (open laughter), Upahasita (Laughter of ridicule), Apahasita (obscene laughter) and Atihasita (Boisterous laughter). The superior types of persons, the middling ones and the base ones have respectively two of these. Smita and Hasita belong to the people of high rank; Vihasita and Upahasita to the ordinary people and Apahasita and Atihasita to the mean people.
For the people of high Rank, the cheeks are slightly blown, the glances are elegant, and the teeth can not be seen, in the Smita. And in Hasita, the mouth and the eyes are blooming, the cheeks are blown and the teeth are slightly seen. For the Middling ones, Vihasita should be befitting the occasion. It is laughter when slight sound is produced sweetly. The actor contracts the eyes and the cheeks. There is cheerful luster in the face. In the course of the Upahasita the nostrils become expanded. The shoulder and the head become a little bent. For the mean People the Apahasita is usually unsuitable to the context. Tears trickle from the eyes. The actor violently shakes the shoulders and the head. The Atihasita is excessively boisterous. The eyes are expanded, tears drop from them and hands cover the sides.
Hasya rasa is an essential part of the Natyashastra. When humorous interludes arise in the course of a dramatic performance the author shall so depict the smile or laughter as the case may be that the superior, middling and the mean do so befittingly.