What does Element mean?

Elements are the fundamental materials of matter, that cannot be chemically simplified (but note that sometimes elements occur as multinuclear molecules that could be transformed into individual atoms of the same type, i.e. ${O}_{2} \rightarrow 2 O$). Each element has a characteristic atomic number, $Z$, which relates to the number of positively charged particles in the element's nucleus. Because elements are by and large electrically neutral, each element has a number of electrons, negatively charged particles of negligible mass, whizzing around the nuclear core.