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Webster 1913 Edition
Porphyrogenitism
Porˊphy-ro-gen′i-tism
,Noun.
[LL.
porphyro genitus
, fr. Gr. [GREEK]; [GREEK] purple + root of γίγνεσθαι
to be born.] The principle of succession in royal families, especially among the Eastern Roman emperors, by which a younger son, if born after the accession of his father to the throne, was preferred to an elder son who was not so born.
Sir T. Palgrave.