Declination

I've seen this word in a few language forums, especially used by foreigners, to mean declension. All the dictionaries I have access to do not assign the declension acceptation to declination, but only mention an astronomical sense. Sometimes from seeing a word being used in a certain one, one may fall into the trap of believing it to be correct usage, which no one has yet been able to prove to me is valid for declination meaning declension. Declination is obviously built on other languages, like Portuguese declinação, Spanish declinación, Italian declinazione, French déclinaison, German Deklination, etc., which have a suffix ação, ación, azione, aison (more commonly ation for French) and ation corresponding mostly to English ation.