Nouns in -ns in Latin regularly inflect by making the -s into -t-, as mons "mountain" plural montes, pons "bridge" pontifex "priest" (the "bridge" between you and God). Sometimes we borrow from Latin either directly or via (Norman) French words derived from different inflections of the same Latin word. Similarly, -r -> -rd- cor "heart" gives us "core" (from the nominative singular cor) and "cordial" (from the adjective cordialis which in turn derives from the genitive cordis); and -rd- -> rs ardeo "I burn" gives us "ardent" from ardere (infinitive) and "arson" from arsus (past participle). (Incidentally "coronary" does not come from cor "heart" despite its connection with cardiology. It comes from corona "crown", the same place as our word for the gaseous envelope surrounding the Sun).

My favourite is "dependent" (adjective) and "dependant" (noun). I have dependent children who are my dependants. All sorts of supposedly learned people get this wrong. Many years ago I had to draft a form involving these two terms (it was asking people about their financial circumstances) and it was sent to a certain civil servant who thought he knew the lot. He amended it so that the two words were spelled arbitrarily, as if the choice of spelling were a matter of taste (although even if that were the case, he should have been consistent). We wrote to him telling him the rule mentioned above, and advising him to spell the form correctly, as I had drafted it. He wrote back that he "was a Grade 7" and therefore his word was law. He then printed and circulated a million copies and sent the resulting letters of complaint to me to answer.

We wrote to his Minister's private office enclosing the correspondence containing our advice and his arse was kicked from one end of the Central Line to the other.

This is quite interesting: [Link]

Edited by chateauferret (10 Apr 2018 10.57pm)

Just adding to this theme, (and continuing the thread drift, sorry!)

The Latin words for left and right, sinister and dexter, were corrupted during the Middle Ages by the hysteria surrounding witchcraft, where anyone who was left handed was assumed to be in league with the devil.

Hence we have dexterous, dexterity (good things), and sinister (bad thing).

In French a “sinistre” can mean a disaster or accident.