Real Dictionary

primary
a complex construction or entity [...]
a liver cell [...]
a person or thing that is first in rank, occurrence, etc [...]
a sketch to show the proposed layout of an advertisement, as in a newspaper [...]
a specialized cell that conducts nerve impulses: consists of a cell body, axon, and dendrites [...]
an arrangement of two or more things in a successive order [...]
any abnormal swelling [...]
any of various proteins produced in the blood in response to the presence of an antigen. By becoming attached to antigens on infectious organisms antibodies can render them harmless or cause them to be destroyed [...]
invasion of the body by pathogenic microorganisms [...]
Primary education is given to pupils between the ages of 5 and 11.
the engine, esp an internal-combustion engine, of a vehicle [...]
the outer layer of any organ or part, such as the grey matter in the brain that covers the cerebrum ( cerebral cortex) or the outer part of the kidney ( renal cortex) [...]
the output of an industrial concern in relation to the materials, labour, etc, it employs [...]
the total of the inherited ideas, beliefs, values, and knowledge, which constitute the shared bases of social action [...]
You use primary to describe something that is very important.