# The X is on vs the X is at? What would you describe this variation as?

"The Knight is on D1." and "The Knight is at D1."

Semantically the sentences mean the same thing. They are describing the position of a knight on a chessboard. The document I am writing contains a lot of these examples. They describe a valid scenario of a chess-style game which will be parsed by a computer program.

e.g.

Given the game has just started
And the Pawn is on E2
And the Knight is at G8
When I move the Pawn to E4
Then I should be shown "Pawn to E4"
And the Pawn should be at E4

I have found myself changing between 'on' and 'at' for what I think is a variation for the sake of readability and to keep the reader engaged. Linguistically, how you describe this variation? Is there an academic term for it? And is there an academic term for keeping the sentences exactly the same?

Note: I am not asking for which style is better or worse. I just want to write about what the difference is. How I would describe it.

• Good question for the Linguistics Q&A. May 4, 2011 at 21:41
• Actually, this is probably most apt for Boardgames.SE May 4, 2011 at 21:46

There is a common sense version for keeping it the same. If you vary the usage, readers will think there is a difference implied.

• I am not asking for which style is better or worse. I just want to write about what the difference is. How I would describe it? May 5, 2011 at 11:20

There is a slight difference between the sentences. If you flesh them out with their exact meaning, you get:

The knight is on the square with the coordinates D1.

and:

The knight is at the coordinates D1.

The first one describes the physical location of the piece on the board, while the second describes it's position in the coordinate system of the board. This difference is of course mostly semantic, and generally there is no practical difference.

When descibing a computer program, I would lean towards using at, just because there are no physical pieces and no physical board to put them on.

• While you are technically correct, the square at D1 is easily referred to as "D1" and not "the square at D1." May 4, 2011 at 21:51
• @MrHen: Yes, that's how you normally use it, but I am talking about what it really means, because that is not so evident from how it's used. May 4, 2011 at 22:44

And is there a an academic term for keeping the sentences exactly the same?

The term could be notation:

a series or system of written symbols used to represent numbers, amounts, or elements in something such as music or mathematics

Or style:

a manner of doing something — a way of painting, writing, composing, building, etc., characteristic of a particular period, place, person, or movement.

Or any of the following (or terms like them):

• invariance
• immutable
• non-changing