diaeresis

1. The logical division of a genus into its species. (Silva Rhetoricae)
2. Dividing one syllable into two (especially the pronunciation of two contiguous vowels). A kind of metaplasm. (Silva Rhetoricae)

3. Division: a figure when one syllable is divided into two parts.; Diaeresis [diairesis] divisio, division. It is a figure of Prosodia, and is when one syllable is divided into two parts. (JG Smith)

4. Diaeresis is another figure of spelling, the separating the vowels that might form one syllable - a diphthong- into two; as aerolite* for aerolite. (Macbeth)

5. Diaeresis in Latine Divisio, is a forme of speech which divideth the generall kind into special kinds, yet not in a dialecticall forme, but in a rhetorical maner for amplification sake. (Peacham)

5. Partitio, is a form of speech by which the orator divideth ye whole into parts. Salomon divideth his whole knowledge thus: “for he hath geven me the true knowledge of the things that are, so that I know how the world was made, & the powers of the elements, the beginning, the end & middest of times, how the times alter, and the change of seasons, the course of the yeare & situation of the starres, the nature of living thigns, the furiousnes of beastes, the power of the winds, the imaginations of men, the diversities of plants, and vertues of roots, & all things both secret and knowen do I know: for wisedome the worker of all thinges hath taught it me.” Sap. 7.17.18.19.20. In like manner he reckneth up, & rehearseth the parts of his prosperity in the 2. chap. of his booke called Ecclesiastes.
Quintus Curcius.
Another: Every nation hath his teame and his plough to get his living, his bed to take his rest, somefrute of his labour for his frend, his bow & his spear for his enemy, his bow to meet him far off, & his speare to wound him nigh at hand, mourning at burials, mirth at mariages, & religious worship in their Temples. here the generall custome of nations is the whole, which as you see is divided into certaine partes. (Peacham)

6. 3. Nature of Division.
The exposition of the extension of a notion is its division. Thus, the notion 'man' includes under it 'white' men, 'black' men, 'red' men, etc., divided according to 'color:' Africans, Asiatics, Europeans, etc., divided according to 'geographical lines;' Jews, Mohammedans, Buddhists, Christians, etc. divided according to 'religion.' It is evident that the character of our division will depend entirely upon the principle according to which we divide a notion into its constituent objects. It follows that a notion cannot be divided when it includes only one object. (Hill)

7. 5. The Diaeresis [**] is sometimes placed over the second of two vowels to show that they are pronounced separately; as, zoölogy, coöperation. (Waddy)

8. Diaeresis one into two divides; By which the smoother measure gently glides. (Holmes)

1. An example of the second definition:
The professor's self-importance could be measured by the way he pronounced "medieval" as "medi-eval." (Silva Rhetoricae)

4. Trench, Archbishop of Dublin, supplies us with a sort of diaersis, or separation, when he uses, with fine effect, "not ever" for ever:

"In palaces are hearts that ask,
In discontent and pride,
Why life is such a dreary task,
And all things good denied.
And hearts, in poorest huts, admire
How Love has, in their aid-
Love that not ever seems to tire-
Such rich provision made." (Macbeth)

4."Before the starry threshold of Jove's court
My mansion is, where those immortal shapes
Of bright aerial spirits live ensphered,
In regions mild of calm and serene air,
Above the smoke and stir of this dim spot
Which men call Earth, and with low-thoughted care
Strive to keep up a frail and feverish being,
Unmindful of the crown that virtue gives."
- Milton (Macbeth)

5. “Aske the cattaile, and they shall inform thee, ye fowles of the aire & they shal tel thee, the increase of the earth, and it shal shew thee, or the fishes of the sea, and they shal certifie thee” Job. 12., by which answere of Job to his frends he declareth ye their wisedome was no other then such as the very brute beastes do daily teach, which he divideth into sundry kinds, wherby he doth pithily & elegantly set forth & amplifie their grosse ignorance. By this figure not only living creatures, but also plants, trees flowers, the lights of heaven, the stones of the earth, mettals & all other such like may be divided into their several kinds, whereby the large and bountifull worke of nature is spread abroad, and many secret causes are plainly discovered and brought into open light. (Peacham)

8. Evoluisset, for evolvisset. (Holmes)