# What is the singular for an octadic?

As I understand the octadic is 8 of something.

In relation to sections, what would be a single section called in the octadic?

The comparison I draw from is the quartile, each 'section' being a quarter.

Is there a similar case for the octadic?

To further explain, what would a shaded section in this picture be referred to as? For a quarter, I would refer to this area as a quartile. Edit: I am aware it may be possible (maybe not) to use 'the eighth'. However, it just doesn't feel correct.

• Could you tell me where you found your definition of octennial? Because the normal definition of octennial means that a single "section" in an octennial is called a year. May 8, 2014 at 13:28
• But in general, on eighth part of a whole is called one eighth. A quartile is a quarter, a quarter is not part of a quartile. If you have a collection of eight items, each part is an item. I suggest you edit your question to clarify what you are actually asking for :) May 8, 2014 at 13:31
• @oerkelens you are correct my mistake this should have been " octadic May 8, 2014 at 13:31
• My dictionary agrees with @oerkelens': an octennial is a set of eight years. I think the word you're after is an octet: "A group of eight people or things". May 8, 2014 at 13:32
• But one part of a set of eight is one, or is my math so wrong now? May 8, 2014 at 13:32

With your picture, I wonder if octile is not simply what you are looking for?

Quarter => quartile
Eighth => octile
Tenth => decile
Hundredth => percentile

• I will use it anyway.. its purely for code commenting on an array.. Much appreciated ! May 8, 2014 at 13:47

For the specific diagram you give, an eighth-part is an octant, using the following senses of the word.

1. The eighth part of a circle; an arc of 45 degrees.
2. (geometry): The eighth part of a disc; a sector of 45 degrees; half a quadrant.

A fourth of the diagram is a quadrant, in the sense “One fourth of a circle or disc; a sector with an angle of 90°”. (More commonly, quadrant has the sense “One of the four sections made by dividing an area with two perpendicular lines” or of being one of the regions of the Cartesian plane that are bounded by the x-axis and y-axis; the “first quadrant” being the region where x>0, y>0; “second quadrant” where x>0, y<0; etc.)

• You hit the nail on the head for the use case. Thank you for such a concise answer. May 8, 2014 at 19:25
• +1, "octant" is the term I've seen used in context where such a term is needed (e.g. with various line drawing algorithms, where the first step is often determining which octant the direction of the line falls in). May 8, 2014 at 21:50

A single section of 8 would be an eighth (notice the extra "H" at the end):

eighth [eytth, eyth]