Which element is not considered a major element in the human body?

In the context of the human body, major elements refer to those that make up a significant portion of body mass and are essential for various biological functions. Oxygen, carbon, hydrogen, and nitrogen are commonly recognized as the four major elements in the body, often referred to as the primary constituents of organic molecules, where oxygen is a critical component of water and various organic compounds, carbon forms the backbone of all organic molecules, and nitrogen is essential for amino acids and nucleotides.

Iron, while important, is classified as a trace element. It plays vital roles, particularly in the transport of oxygen as part of hemoglobin in red blood cells and in certain enzymatic processes. However, it constitutes a much smaller proportion of the body's mass compared to the major elements. Thus, in choosing which element does not belong to the category of major elements in the human body, iron stands out, as it is needed in lesser amounts compared to the others mentioned.