I am working on modeling a problem for a computer program and am having a tough time coming up with the proper naming convention I would like to use.

Specifically I am working with a finite state machine that can have multiple levels of states. For parent states we usually use "parent" or "super" (i.e. super state) and for child states we use "child" or "sub-" (i.e. sub-state)

I have run into the problem of what to call a state transition to a state that is on the same level. I am not exiting to a parent state and I am not entering a child state. I am essentially moving sideways or swaping out the current state for another one that could be treated as a child state of the existing parent.

Here is an example

Current state list: State1, State1.1, State1.1.1

Exit the current child state.

New state list: State1, State1.1

Swap over to child 2 state.

New state list: State1, State1.2

What prefix or descriptor would I use when comparing State1.1 and State1.2?

  • The only things that comes to mind immediately are "co-" as in co-state and sibling state. The latter would work with parent and child, but co- does not seem to be the proper fit unless I mis-understand the meaning of it. (Barmar's answer is a little more descriptive) – MrJman006 Apr 27 '15 at 20:42
  • Possibly a peer state? – WS2 Apr 27 '15 at 20:46
  • How about "homo-"? – Hot Licks Apr 27 '15 at 20:51
  • 1
    You're looking for the prefix iso-. – Dan Bron Apr 27 '15 at 21:28
  • I agree with @DanBron, an isostate is one that's on the same level as another. – Gnawme Apr 27 '15 at 21:47

You continue the family metaphor. A higher level is a parent, a lower level is a child, so an equal level is a sibling.

I'm not sure there's a prefix analogous to super- and sub-, though. The best I can think of is co-, but costate doesn't sound right.

  • Hahaha I just was posting this as a comment to my question as you answered! – MrJman006 Apr 27 '15 at 20:43
  • And should you need to relate more than 3 levels (parent, sibling, child) with each other, you could continue the family metaphor by using "ancestor" for something higher and "descendant" for something lower. As a programmer, you may already be familiar with this convention from CSS syntax. – Quillmondo Apr 28 '15 at 0:16
  • This was answer was the one that sounded most natural when following the family metaphor, but the comment on the original question suggesting iso- would probably be the closest to what I was actually looking for. – MrJman006 May 8 '15 at 20:22
  • OK, but I suggest you say "isostate" to some people in your intended audience and see if they understand you. – Barmar May 8 '15 at 20:24


coequal states



: equal with one another (as in rank, power, age, or extent)

a confederacy of coequal sovereign states — S. E. Morison & H. S. Commager

Merriam-Webster Unabridged Dictionary


Public Administration: Policy, Politics, and Practice - Page 111 William C. Johnson - 1996

The requirements traditionally attached to assistance programs may be viewed as part of a contractual agreement between two independent, coequal levels of government. ...

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