This is a research question in the history of math, I suppose.


As a non-native english speaker I became used to mathematical expressions like 'dynamical' and 'tangential'. When using them in daily conversation as substitutes for 'dynamic' and 'tangent' I got frowned upon by native english speakers who claimed to have never heard of these words before.


Some references suggest


<https://www.merriam-webster.com/dictionary/dynamical>


<https://www.merriam-webster.com/dictionary/tangential>


that indeed they **can** almost mean the same as 'dynamic' and 'tangent' but for some reason nobody seems to use these words that way.


So whereas in English:


A dynamic person-a dynamical system


the adjective is different


it is in French


une personne dynamique- un système dynamique


and in German


Eine dynamische Person - ein dynamisches System


the adjective is the same.


I am wondering when (and maybe also why) these expressions started deviating in English.



Why is a dynamical system not a dynamic system?
Here are the two entries from Anthony Lo Bello's *Origins of Mathematical Words* (John Hopkins, 2013) which is very informative, entertaining, and perhaps curmudgeonly. In his parlance, following the lexicographer Samuel Johnson, a "low word" is one with an "irregular combination" of roots that has "little or no etymological legitimacy."


**dynamical** The Greek noun *[dunamis]* means *power*. The corresponding Greek adjective is *[dunamikos]*, *pertaining to power*. The correct English adjective is therefore *dynamic*. To superimpose the vestige *-al* of the Latin adjectival ending *-alis* upon the stem of a Greek adjective is often the product of ignorance and produces a low word. In other cases, the addition of the Latin suffix to the Greek adjective is due to the fact that a different meaning is intended from that of the Greek adjective; thus, *dynamic* was an established word, so one spoke of *dynamical systems* rather than *dynamic systems* to avoid confusion.


**tangential** See the entry **tangent**. The Latin adjectival suffix *-alis* was added to the stem of the participle *tangens*, *tangentis*, which was already an adjective but felt to be a noun, *the tangent*.


