English word solidarity comes from Latin solidus, and later French solidaire (Interdependent. Solidary, showing solidarity (with).). The root Latin form ultimately derives from Indo-European *solh₂- (integrate, whole).
Solid (Medieval, historical) A bezant: the solidus's debased Byzantine successors.. (Medieval, historical) A shilling, as a unit of account or silver coin.. (historical) A solidus: a Roman ~23-carat gold coin introduced by Diocletian in AD 301.
(countable) A bond of unity or agreement between individuals, united around a common goal or against a common enemy, such as the unifying principle that defines the labor movement; mutual support within a group.. (uncountable) Willingness to give psychological and/or material support when another person is in a difficult position or needs affection.