Definition of primordium in US English:



  • An organ, structure, or tissue in the earliest stage of development.

    ‘the primordium of the pituitary’
    ‘the axils of the leaf primordia’
    • ‘The development is initiated as a hyphal knot of 0.2 mm or less in diameter, which rapidly develops into a tiny primordium containing the rudimentary tissues of the future pileus and stipe.’
    • ‘These organ primordia, which develop after a period of time corresponding to winter in temperate regions, are called preformed organs.’
    • ‘In flowers, both genes are expressed throughout inflorescence and floral meristems and in developing organ primordia.’
    • ‘Microscopical examination for the fungal infection was performed on the bristles, adjacent hypocotyl surface and the internal tissue of root primordia.’
    • ‘Although mitoses were still detected in leaf primordia of that stage, cell differentiation had already started.’


Late 19th century: from Latin, neuter of primordius ‘original’, from primus ‘first’ + ordiri ‘begin’.