2516: Rhotacism & Dissimilation Nov 2, 2021

The word 'meridian' in English, or more directly even 'ante/post meridiem' (a.m./p.m.) is from the Latin word 'merīdiēs' meaning 'midday; noon'. This is from a corrupted phrase 'medīdiēs' which is just an contraction of 'medius' (middle) and 'diēs' (day). The R in the middle of 'merīdiēs' therefore is a bit odd at first glance. In fact, this is a fairly normal occurrence of rhotacism in the transition into Classical Latin. This normally happens to the sounds [s] or [z]—not [d]—that they should turn into [r] and really this is a process of dissimilation because it is followed by another [d].