This is the word for ‘dot’, and in this sentence refers specifically to the dot that occurs under long vowels and doubled sonorants.
Creating this word, I thought I was using an unclaimed stem syllable, but when I checked the dictionary to make sure, I found that the word for ‘kidney’ used the same stem, and I decided that would not do. So I changed the word for ‘kidney’ to use the (probably unrelated) stem –sēss-. This makes the pronunciation of ‘dot’ [ja zeː za] and ‘kidney’ [sa zeˑs sĕ]. This led to a tongue twister I will share with you later.
temme ē jaþēλi ien jakā ānen ansāorīki ien jaxūna ānen anrūēli ī xiēn jē jāxīsse jīlke ī jāo ja la sūjatā ē jāo sūjōl ien jiēxa ānen jasēsi ī jōrrisi ē jatatēn ien ñi jīlkena cē jaþārre ōrra ē jawāññerāñi jīþi nā ī;
He said to him the ideas: the doings of consonants; the pattern of vowels, and also concerning the writing line and that which is beneath it and that above it; the usefulness of dots…