In plants, "parenchyma" is one of the three main types of ground tissue, and the most common. It can be distinguished through their thin cell wall as compared to other cells. Parenchyma cells make up the bulk of the soft parts of plants, including the insides of leaves, flowers and fruits (but not the epidermis or veins of these structures).
The parenchyma are the functional parts of an organ in the body. This is in contrast to the stroma, which refers to the structural tissue of organs, namely, the connective tissues.
In the brain, the parenchyma refers to the functional tissue in the brain that is made up of the two types of brain cell, neurons and glial cells. Damage or trauma to the brain parenchyma often results in a loss of cognitive ability or even death.