To start with, the cell as we obtain it from the cell theory , is perhaps the most important structure that allows our primary inter-phase with the intricacies of the biological world, the complexities in form and function, but the mere reduction in size ,yet forming the building block for a human with trillions of cells.
So how do you define a cell?
In a nutshell it can be defined as the unit of the living system or as an unit that makes up the living body. But if one is a little careful to provide a holistic or complete definition ,then he or she might want to say that it is
protoplasmic mass bounded by a plasma membrane with cytoplasmic organelles and nucleus with DNA (except mature Red blood cells ), that can perform all physiological activities of survival and reproduce(except nerve cells).