Decreased mathematical ability due either to a learning disorder or damage to the brain.
Example: A professor of mathematics, under treatment for brain trauma after a car accident, discovers he can no longer figure a fifteen percent tip.
Here is a great website that allows people to see a comprehensive list of all of the symptoms associated with dyscalculia, it also has treatment options and prevention methods: http://www.dyscalculia.org/calc.html
Fournier, G. (2010). Dyscalculia. Psych Central. Retrieved on October 4, 2015, from http://psychcentral.com/encyclopedia/2008/dyscalculia/