Hi! I was working with a student today, and we came across the word "existence." We could hypothesize a prefix (-ex) and suffix (-ence), but weren't sure of the base. (Previously, we had talked about <ist> as a suffix meaning "one who," so when he saw the <ist> here, he wondered if it was that suffix.)
After looking at "existence" in etym, we saw that the roots are spelled with and without the <s> from "sistere." Here is the entry...
late 14c., "reality," from Old French existence, from Medieval Latin existentia/exsistentia, from existentem/exsistentem (nominative existens/exsistens) "existent," present participle of Latin existere/exsistere "stand forth, come out, emerge; appear, be visible, come to light; arise, be produced; turn into," and, as a secondary meaning, "exist, be;" from ex "forth" (see ex-) + sistere "cause to stand," from PIE *si-st-, reduplicated form of root *sta- "to stand, make or be firm."
We talked about that in English <s> doesn't follow <x>, so it would make sense that we don't have the <s> in English. But I wondered about a word sum. What do you think about this word sum that represents the <s> from the root?
ex + (s)ist + ence -> existence
(Also in our session today, he asked about the word, "crap." This of course led to the "discovery" that another word related to "crap" is related to "science." Sometimes it's just good to go with his interests... it makes for an interesting/careful discussion. (We also talked about using these words.))