2560: Iotacism Dec 16, 2021

Iotacism, also referred to as 'itacism' describes the shift of diphthongs or groups of vowels converging into the [i] sound. This pattern is not named for a speech impediment like with sigmatism or lambdacism, but for communitywide sound-shifts as on the naming pattern of rhotacism or zetacism. Greek is notable for its iotacism, since in Modern Greek, the letters and letter pairs which used to represent all totally different sounds ι, η, υ, ει, οι, υι are all said now as [i].

2559: Sigmatism Dec 15, 2021

Although many conditions and linguistic phenomena are named with a Greek letter plus '-cism', they aren't always named for the same reasons. 'Sigmatism', like 'lambdacism' describes a speech impediment that regularly affects one sound, in this case [s], though that can denote either the over- or underproduction of it. This can be an appropriate term to describe the effect of a lisp, though not necessarily.