ex·ter·nal·i·ty 
(ĕk′stər-nălĭ-tē)
(ĕk′stər-nălĭ-tē)n. pl. ex·ter·nal·i·ties
1.
a. The condition or quality of being external or externalized.
b. Something that is external.
2. A cost or benefit that affects people other than those involved in the economic activity that produced it and that is not reflected in prices: pollution and other negative externalities.