BG Chap 13 - The composition of the field
Kṛṣṇa next says that He would briefly describe the composition of the field, its transformations, its origin or purpose, the identity (svarūpa) of the knowers of the field, and their influence and powers.
The field along with its transformations is said to consist of the five gross elements: ether, air, fire, water and earth; false ego or ahaṅkāra, called tāmasaḥ bhūtādi, which is the cause of the five elements; buddhi (intelligence) which here means mahat-tattva, predominated by jñāna, which is ahaṅkāra’s cause; avyakta, which means prakṛti or pradhāna, containing three guṇas, and which is the cause of mahat-tattva; the ten senses (five knowledge and five action senses), which are the products of ahaṅkāra in the mode of passion; mind, the internal sense, the product of ahaṅkāra in the mode of goodness; the five sense objects (tanmātrās) – sound, touch, form, taste and smell. The sense objects are subtle in form, being situated between the ahaṅkāra and the gross elements, and are manifested as qualities of the gross elements. For instance sound manifests as the quality of ether. These tanmātrās become gross as the objects of perception by the senses. That which is composed of these 24 elements is known as the field (body). The five gross elements, false ego, mahat-tattva and pradhāna are the basic components of the field. The senses such as the ear and the sense objects such as sound are what take shelter of the field.