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In the Wikipedia article for Freemasonry, it gave a picture regarding the emblem of the Freemasons:

enter image description here

The caption below reads:

The Masonic Square and Compasses.
(Found with or without the letter G)

Just wondering, is "Compasses" correct? Shouldn't it be compass? I looked this up on several dictionaries, and I don't seem to find "compasses" when referring to a tool for drawing circles, only "compass". However, "compasses" makes sense, as it looks something similar to "scissors".

Should it be "compass" or "compasses"?

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Just to point out that the instrument shown would now be called `a pair of dividers'. It is at least possible that the name changed when a pencil was attached in place of one leg, and so the instrument was not so obviously bifurcated. – TimLymington Aug 30 '11 at 10:20
In one of my high school math classes (ca 1963) the instructor quite firmly asserted that the instrument you used to draw circles was "a pair of compasses" rather than "a compass". I don't recall anyone advocating "compasses" before or since, however (though I've completely blocked from my memory my freshman college drafting class). No idea what current US school usage is. – Hot Licks Nov 23 '15 at 2:39
up vote 7 down vote accepted

I think it is not a typo. I've looked up compasses in my Babylon English dictionary, and it says:

n. instrument for drawing circles and measuring, calipers.

Additionally, Oxford Dictionaries Online states there is also compasses or a pair of compasses.

2) (also compasses or a pair of compasses) an instrument for drawing circles and arcs and measuring distances between points , consisting of two arms linked by a movable joint , one arm ending in a point and the other usually carrying a pencil or pen.

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So, it's just an alternative spelling? – Thursagen Aug 25 '11 at 11:52
My understanding is that it's an alternative spelling which is more apprehensible. I believe, without clear context, compass alone connotates navigational instrument that shows directions. – Mehper C. Palavuzlar Aug 25 '11 at 11:59
I remember way back in school, on the first day of geometry class, the teacher told us the supplies we would need, including "a pair of compasses". Needing TWO of them seemed strange to me! What, we would use one in each hand? But then the teacher went on to explain that "a pair of compasses" was the long way to refer to that particular geometric drawing instrument. – GEdgar Aug 25 '11 at 12:36
Using compass in the singular, unless it refers to a device for navigation, still sounds odd to my British ears after 20 years in America. – Kevin Lawrence Aug 25 '11 at 23:36
@Kevin - agreed - UK usage is definitely "compasses" for the drawing or map-measuring tool, "compass" for something that points north. – AAT Aug 26 '11 at 23:34

A compass, like scissors, tweezers, glasses, pliers, tongs, bellows, and calipers, is an instrument that is made up of two near-identical pieces that are attached to each other. Comparing it with these examples, it's somewhat surprising that we generally refer to it in the singular rather than in the plural. All three constructions: a compass, a pair of compasses, and compasses, are acceptable, although a compass is currently the general usage. As this Google Ngram shows, the plural compasses was formerly used much more often than it is now:

enter image description here

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how has your Ngram distinguished between uses of compass to mean a drawing / measuring instrument, and uses to mean a navigational aid? If it didn't make that distinction it is not very helpful. – AAT Aug 26 '11 at 23:35
The Ngram compares the phrases "compass to draw" and "compasses to draw." It's really hard to fit the nativational aid into this phrase. If you have doubts about this Ngram, the Ngram for the phrases ruler and compass(es) shows the same behavior. – Peter Shor Aug 27 '11 at 0:21
OK thanks, I had missed the small print on the ngram label: adding "to draw" should have helped to limit this to references to drawing instruments. – AAT Aug 27 '11 at 22:42

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