Tṛṣṇa is often translated as ‘thirst’. This is often misunderstood or not understood at all. Is it just thirst? What is it?
Tṛṣṇa – it is āgneya vyādhi wherein agni vaiṣamya takes place. It is defined as “tālu prapannam janayed pipāsa”. what is pipāsa? – pipāsa is not thirst. Thirst is a need for something eg. Water. If that need is in the tālu it is tṛṣṇa – [What is tālu? tālu is the region of śrṅghāṭaka marma – what is this marma? – it is a sirā marma] In other words it is crying of the drying nerves coming from the tālu. Now, what is the name of the disease in nānātmaja where the siras are involved? – see sirā graha. It is defined as “raktam āśritya pavanaḥ”. sirā vyādhi is a nānātmaja vyadhi where the ātma guṇa of vāta is affected. It is kevala vataja and sira is affected. Further, “kuryān mūrdhatarā sirāḥ rūkṣāḥ”. It means śoṣaṇa and it is a cry from the mūrdha tara sirā. Any śoṣa (depletion) of the mūrdhatara siras can be called tṛṣṇa. It is not just thirst. Thirst is a normal physiological phenomenon.