विपर्यास

पुं० [सं० वि+परि+अस् (होना)√घञ्] [वि० विपर्यस्त] १. विपर्य्यय। उलट-पलट। व्यतिक्रम। २. जैसा होना चाहिए, उसके विरुद्ध कुछ और ही हो जाना। ३. भ्रम। भ्रांति

Desires that are considered abnormal or unacceptable are called perversions.

There is a remarkable contrast between the twins.The contrast of light and dark shade counts a lot in painting.