What term describes the lack of development of an organ or tissue?

The term that specifically describes the lack of development of an organ or tissue is aplasia. Aplasia refers to a situation where an organ or tissue is completely absent due to a failure in development during the embryonic stage. This can occur when there is an issue during the differentiation of cells that would normally form the organ or tissue.

In contrast, other terms refer to different processes related to tissue and organ development. Hypertrophy refers to the increase in size of an organ or tissue due to the enlargement of its cells, indicating that the tissue is developing but growing larger. Hypoplasia indicates an underdevelopment or incomplete development of a tissue or organ, suggesting that while some development has occurred, it is insufficient. Dysplasia refers to the abnormal growth or development of cells within a tissue, often leading to structural abnormalities, but it does not imply a complete lack of development either.

Thus, aplasia is the most accurate term for the complete absence of organ or tissue development, distinguishing it from conditions where some degree of development exists.