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From online records they appear to be interchangable.
Example : Bridget Carden spinster daughter of "James Gilmartin" a Herd married Martin Morrison in 1879. She applied for a pension about 1909, stated her name was Bridget Caden now Mrs Bridget Morrison of Ellamore, Bonniconlon. At that time the 1851 census was reviewed to see her stated age in 1851 to she if eligible for pension.