Being very important, or key to something.
Having or containing the centre of something.
Being in the centre.
Exerting its action towards the peripheral organs.
centre
Acting to cause or connect.
occurring during the course of a disease.
Having a primary hue (red, blue, or gold), as opposed to one that can be created by mixing colors with primary hues.
Defining or inferring a generalization or category of meaning.
Intermediate.
An intermediary or go-between; Something or someone that passes information, instructions, or influence between one person or thing and another person or thing.