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
Particular, characteristic.
Of a rare quality, unusual.
Being the only one of its kind; unequaled, unparalleled or unmatched.
Of a feature, such that only one holder has it.
A thing without a like; something unequalled or unparallelled; one of a kind.