​Ordinal-Linguistic Personification is a form of Synesthesia in which sequences such as ordered numbers, calendar days, and letters are associated with very specific personalities.

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Often comorbid with Grapheme Synesthesia, OLP is also consistent over extensive periods of time.​

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Research has yet to determine a definitive cause for this form of Synesthesia, though most hypotheses claim it is due to the cross-wiring of angular gyrus (processes ordinal sequences) and adjacent areas in the supramarginal gyrus.