Which concept is defined as a social system where power has historically been…

Concept: Patriarchy refers to a social system in which power — political, economic, and social — has historically been concentrated in the hands of men, structuring authority, decision-making, and property or inheritance rights around male lineage and control, while women are systematically excluded from these positions of power, producing durable, unequal social relations between genders.

Application: The stem describes exactly this system: power historically held by men, systematically depriving women, and maintaining unequal social relations. This is the defining description of a patriarchal system, so "Patriarchal system" is the option that matches the definition.

Contrast: Compare with the other terms offered:

• Egalitarian principle describes an ideal of equal status and rights across genders — the absence of the power imbalance in the stem, i.e., the opposite pattern.

• Matrilineal descent is a kinship-reckoning convention where lineage, family name, and inheritance are traced through the mother's line; it concerns how ancestry is traced, not how political or social power is distributed.

• Matriarchal structure denotes a social system where women, not men, hold the central positions of authority and leadership — again the inverse of the power arrangement described in the stem.

Cross-check: Only the patriarchal-system definition satisfies both criteria in the stem — power historically concentrated with men, and systematic deprivation of women that maintains unequal social relations.