Definition: The term "virol" refers to viruses. Viruses are a group of microorganisms that have the ability to replicate themselves, and can cause disease or harm to living organisms. There are over 10,000 known types of viruses, which are classified based on their size, shape, type, and infectivity (ability to reproduce). Viruses include DNA viruses (such as HIV), RNA viruses (such as the influenza virus) and more recently evolved spike proteins, which act like viral capsids, making them capable of entering human cells and causing disease. Viruses can also be classified by their pathogenicity, which refers to how they cause disease or infection in living organisms. In summary, "virol" is a term used to describe viruses, which are microorganisms that have the ability to replicate themselves and cause illness or harm to living organisms. The word has been widely used to refer to a variety of different types of virus, including those that infect human cells.