Prognosis and diagnosis ------------------------
The two terms prognosis and diagnosis come to us from ancient Greek and are constructed in an analogous way. The Greek adverb and preposition pro carries both a spatial and a temporal sense, the temporal one marking precedence in time. The prefix dia, found in diagonal but also in diabetes and dialysis, originally meant to divide and, by extension, through.
The second part of these terms comes from the Greek adjective gnôstikos, which describes the act of knowing. But why does the spelling of these two words diverge in French? Prognosis is a loanword, via Latin, introduced into Old French toward the end of the 13th century, whereas diagnosis comes directly from Greek and only appears in our language four centuries later.
At the very outset, both terms had a purely medical meaning. Hippocrates himself had written a work called ta prognostika, paving the way for assessing the course of a disease and its chances of recovery. Nowadays, a prognosis is determined through statistical methods on patients who had previously presented the same symptoms. Diagnosis, of course, precedes prognosis.
Both terms have now entered everyday vocabulary, but the first nonetheless remains more sophisticated, leaving the second a wider audience, especially in sporting circles.