Is there an analogous word to "quadrants" but used when something is divided into nine pieces? [duplicate]

If you take a rectangle and divide it into four equal pieces with two perpendicular lines, you have created quadrants:

But what if you divide the rectangle into nine equal pieces with two sets of two mutually parallel lines like this:

Is there a name for these pieces? An example sentence would be:

The dart has struck the middle ______.

If there are six pieces they can be called sextants, and if there are eight pieces they can be called octants, but the word "nonant" doesn't seem to exist, at least not with this meaning.

edit: I'm specifically looking for a mathematical term to refer to the area that the rectangle is divided into, so a word analogous to "quarter" but referring to nine pieces doesn't answer my question. (See this.)

Consider ninth, which means

each of nine equal parts into which something is or may be divided.

It is used to refer to the kind of section you're after in this mathematical text, albeit with scare quotes. Also, "middle ninth square" is used here.

In your sentence:

The dart has struck the middle ninth.