parenchyma
1. A plant tissue consisting of roughly spherical relatively undifferentiated cells, frequently with air spaces between them. The cortex and pith are composed of parenchyma cells (see ground tissues).

2. Loose connective tissue formed of large cells. Its function is to pack the spaces between organs in some simple acoelomate animals, such as flatworms (Platyhelminthes).

parenchyma In plants, tissue composed of the least specialized of plant cells with a system of air spaces running between them. Parenchyma cells are regarded as the basic cells from which all other cell types have evolved; they form a large part of the bulk of many organs.

parenchyma In Platyhelminthes, the tissue, composed of cells and intercellular spaces, that fills the interior of the body. In other animals, the essential cells of an organ, as opposed to blood cells, cells of connective tissue, etc.

parenchyma (anat. and zool.) substance of the liver, etc.; (bot.) cellular tissue. XVII. — Gr. parégkhuma, -mat- ‘something poured in besides’, f. PARA-1 + égkhuma infusion, f. egkheîn, f. EN-2 + kheín pour.
Hence parenchymatous XVII.

parenchyma (pă-renk-im-ă) n. the functional part of an organ, as opposed to the supporting tissue (see stroma).