It is necessary to understand the definition of the bhava in order to understand it and to know its original source to know its definition.
There are a large number of subtle centres inside our body. The original centre is the soul (atma). The soul is encircled by kashaya. Kashaya vibrates with the soul. The vibrations of adhyavasaya influence the leshya (psychic colours). The vibrations of the leshya into the body and give rise to the bhava. This is the long series and long process of the creation of the bhava.
The encirclement of the soul is called kashaya. After the encirclement of kashaya it is known as the centre of a consciousness. Its name is adhyavasaya, the subtle consciousness. There is a mention of unconscious in Psychology. Subtler ever than the unconscious is the world of adhyavasaya.
Each adhyavasaya has many aspects. But there is harmony among them in the sense that those adhyavasayas are vibrated and their vibrations create a new world of leshya. When the vibrations of those leshyas enter the subtle world and come into contact with the chitta, the system of the bhava is created.