What is the term for a specialized structure within a cell?

An organelle refers to a specialized structure within a cell that has a specific function. Organelles play various roles in cellular processes, such as energy production, protein synthesis, and waste management. Examples of organelles include the nucleus, mitochondria, and endoplasmic reticulum, each contributing to the overall function and maintenance of the cell.

The term 'membrane' refers to the protective barrier that surrounds and contains the contents of a cell, regulating what enters and exits, but it does not refer to a specialized structure within the cell itself. 'Tissue' is a collection of similar cells that work together to perform a specific function in an organism, and is a higher level of organization beyond the cellular level. 'Matrix' generally refers to the material or tissue in which more specialized structures are embedded, but it does not specifically denote a structure within a cell. Hence, organelle is the precise terminology for the context of the question.