Question

red blood cells have no nucleus but why do we call them cell

Answer 1

  Because they did have a nucleus during their development, they just expelled it at a later stage of this development. They are just enucleated cells..
there is was also twwo tyes of cell
prokayotic and euaryoktic cells
euarkyotes means which has nucleus during development
prokaryotes means which doesn't have nucleus

Answer 2

RBCs contains nucleus at certain stage but as it mature it lose the nucleus. It is not necessary that a cell lacking nucleus couldn't call a cell. Presence of the nucleus will arise the problem of oxygen transportation & thus its a enucleated cells..