Exogamy

The custom of marrying outside a social class, community, clan, tribe or other social unit.

 

    The fusion of reproductive cells from distantly related or unrelated individuals; outbreeding; cross-pollination.

The opposite of exogamy is endogamy.

  

Heterochromia

In anatomy, heterochromia refers to a difference in coloration, usually of the iris but also of hair or skin. Heterochromia is a result of the relative excess or lack of melanin (a pigment). It may be inherited, or caused by genetic mosaicism, disease, or injury.

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Heterochromia of the eye (heterochromia iridis or heterochromia iridum; the common wrong form "heterochromia iridium" is not correct Latin) is of two kinds. In complete heterochromia, one iris is a different color from the other. In partial heterochromia or sectoral heterochromia, part of one iris is a different color from its remainder.

Eye color, specifically the color of the irises, is determined primarily by the concentration and distribution of melanin. The affected eye may be hyperpigmented (hyperchromic) or hypopigmented (hypochromic).[5] In humans, usually, an excess of melanin indicates hyperplasia of the iris tissues, whereas a lack of melanin indicates hypoplasia.  (definition from Wikipedia)  

Propinquity

Propinquity is a noun meaning nearness in place or time or relationship; kinship; similarity in nature.  In social psychology, propinquity is one of the main factors leading to interpersonal attraction. It refers to the physical or psychological proximity between people. Propinquity can mean physical proximity, a kinship between people, or a similarity in nature between things ("like-attracts-like"). Two people living on the same floor of a building, for example, have a higher propinquity than those living on different floors, just as two people with similar political beliefs possess a higher propinquity than those whose beliefs strongly differ. 

So those who have a mutual interest in words and their meanings have a higher propinquity than exists between those who are interested and those who are not.

Indefectible

Monica recently bought a rucksack that was described on its wonderful label as 'indefectible'.  Hwne I saw that I assumed it was one of those made-up words that translators occasionally manage to create from a mangle of similar words. I was wrong.  It is a real word.

Indefectible adj. - Having the ability to resist decay or failure;  lasting;  having no flaw or defect;  perfect.

I just wish I were indefectible!

In a religious context the indefectibility of the Church is a gift from Christ to the Church by which she is preserved to the end of the age as the "institution of salvation".