Incomprehensibilities refers to things that are hard to comprehend or understand. (We’re pretty sure most of these words qualify.)

Pseudohermaphroditism refers to the condition of having the gonads and karyotype of one sex and external genitalia that is of the other sex or is ambiguous.

And finally, psychoneuroimmunology refers to a branch of medicine that deals with the influence of emotional states and nervous system activities on immune function.

(Did you count only 20 words in the list? The 21st is hippopotomonstrosesquippedaliophobia, which is fear of long words. Apologies to anyone who suffers from this condition with its 36-letter name—we’re sure we’ve made it worse.)