# Same item, different field, different terms
**URL:** https://boards.straightdope.com/t/same-item-different-field-different-terms/729529
**Category:** In My Humble Opinion
**Created:** [August 31, 2015, 7:48pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529 "2015-08-31T19:48:37Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)
#### Post date: [August 31, 2015, 7:48pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/1 "2015-08-31T19:48:37Z")
It’s always cracked me up and/or annoyed me that relatively simple electrical and electronic components are known by peculiar names in some fields.
The classic one is the “condenser” in a car’s point-type ignition. Yes, condenser was the old-old school term for them, but the rest of the world knows them as capacitors.
In doing some AC work recently, I discovered that the black box that goes on the outside compressor unit and allows the 24VAC control system to switch its high power on and off is called… no, not a relay, which is what most of the world calls it. Nope. In HVAC, it’s a “contactor.” Sometimes a “magnetic contactor,” as if there’s any other kind of electrically-operated relay.
A couple of others are lingering on my memory but I can’t bring them to mind. Oh, yeah - “solenoid” for a heavy-duty switch.
Got others?
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [August 31, 2015, 8:29pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/2 "2015-08-31T20:29:57Z")
I thought a solenoid was an electromagnetic actuator (which may operate a switch, valve or mechanical linkage etc).
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### Author:  [@Greg\_Charles](https://boards.straightdope.com/u/Greg_Charles)
#### Post date: [August 31, 2015, 8:54pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/3 "2015-08-31T20:54:02Z")
It’s not exactly an “item”, but the square root of -1 is usually denoted as i by mathematicians, but j by engineers.
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [August 31, 2015, 9:04pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/4 "2015-08-31T21:04:25Z")
**Router** , used in woodworking, communications, and many other industries for different concepts.
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [August 31, 2015, 9:06pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/5 "2015-08-31T21:06:03Z")
> [@Mangetout](#):
>
> I thought a solenoid was an electromagnetic actuator (which may operate a switch, valve or mechanical linkage etc).
Yeah, the whole switching mechanism is referred to as a solenoid often, but it’s still a switch that uses a solenoid.
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### Author:  [@Mangetout](https://boards.straightdope.com/u/Mangetout)
#### Post date: [August 31, 2015, 9:12pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/6 "2015-08-31T21:12:29Z")
> [@TriPolar](#):
>
> **Router** , used in woodworking, communications, and many other industries for different concepts.
Interestingly, pronounced differently in British English - networking; rhymes with ‘hooter’ - woodworking; rhymes with ‘outer’
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### Author:  [@boffking](https://boards.straightdope.com/u/boffking)
#### Post date: [August 31, 2015, 9:42pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/7 "2015-08-31T21:42:32Z")
If you are working behind the scenes of a movie or play, a wooden clip is a C-47 and not a clothespin.
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### Author:  [@74westy](https://boards.straightdope.com/u/74westy)
#### Post date: [August 31, 2015, 9:51pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/8 "2015-08-31T21:51:44Z")
Grey plastic tape is duct tape unless you’re in theater then it’s gaffer’s tape.
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### Author:  [@boffking](https://boards.straightdope.com/u/boffking)
#### Post date: [August 31, 2015, 9:56pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/9 "2015-08-31T21:56:28Z")
> [@74westy](#):
>
> Grey plastic tape is duct tape unless you’re in theater then it’s gaffer’s tape.
Gaffer tape has a cloth backing. It is not the same as duct tape.
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### Author:  [@TriPolar](https://boards.straightdope.com/u/TriPolar)
#### Post date: [August 31, 2015, 10:37pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/10 "2015-08-31T22:37:15Z")
**Brake** has a number of different meanings, some may be related. It can be a device for bending metal, a device for breaking up soil although still spelled ‘brake’, and the modern concept of a stopping device. Some of these forms may have similar roots.
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### Author:  [@BrotherCadfael](https://boards.straightdope.com/u/BrotherCadfael)
#### Post date: [August 31, 2015, 11:06pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/11 "2015-08-31T23:06:01Z")
> [@boffking](#):
>
> If you are working behind the scenes of a movie or play, a wooden clip is a C-47 and not a clothespin.
A wooden clip is a [DC-3](https://en.wikipedia.org/wiki/Douglas_C-47_Skytrain)???
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### Author:  [@Derleth](https://boards.straightdope.com/u/Derleth)
#### Post date: [September 1, 2015, 12:19am UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/12 "2015-09-01T00:19:45Z")
> [@Greg\_Charles](#):
>
> It’s not exactly an “item”, but the square root of -1 is usually denoted as i by mathematicians, but j by engineers.
This is because, for an engineer, the letter ‘i’ is used for electrical current, which begins with the letter ‘c’.
I have one from medicine: The unit of volume in medicine is the ‘cc’, or cubic centimeter. This is what the entire rest of the metricated world knows as the mL, or milliliter, but the medical people in my experience are not changing, and will happily work in thousands of ccs instead of switching to liters. (Litres are Right Out.)
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### Author:  [@Civil\_Guy](https://boards.straightdope.com/u/Civil_Guy)
#### Post date: [September 1, 2015, 1:04am UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/13 "2015-09-01T01:04:09Z")
I chanced to meet an Australian while riding on Amtrak a couple weeks ago. While we were talking about this and that, he mentioned something about how many kilowatts he was saving though some home improvement or other: he then looked at me a little uncertainly as though I might not be used to that unit of measurement, it being metric and all. I assured him that yes, Americans use that for electricity… but usually use horsepower for other power measurements. Thankfully, he did not ask why. I sure as heck couldn’t say why.
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### Author:  [@JWT\_Kottekoe](https://boards.straightdope.com/u/JWT_Kottekoe)
#### Post date: [September 1, 2015, 2:51am UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/14 "2015-09-01T02:51:32Z")
Actually, the j used by electrical engineers is equal to -i, as used by physicists.
On a related note, I find it annoying when a technical term is appropriated by the mainstream to mean something different, for example: “organic”, “growing exponentially” and “quantum leap.”
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### Author:  [@usedtobe](https://boards.straightdope.com/u/usedtobe)
#### Post date: [September 1, 2015, 5:42am UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/15 "2015-09-01T05:42:23Z")
> [@JWT\_Kottekoe](#):
>
> Actually, the j used by electrical engineers is equal to -i, as used by physicists.
>
> On a related note, I find it annoying when a technical term is appropriated by the mainstream to mean something different, for example: “organic”, “growing exponentially” and **“quantum leap.”**
Actually, I find this one incredibly amusing.
(‘quantums’ don’t leap very far, actually).
Another good one is “Light Year” as a unit of exceedingly large times.
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### Author:  [@Bad\_News\_Baboon](https://boards.straightdope.com/u/Bad_News_Baboon)
#### Post date: [September 1, 2015, 9:59am UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/16 "2015-09-01T09:59:39Z")
I think some are getting confused here. The OP is asking for an item that has different names in different fields, not words that are used differently.
The only thing I can think of off the top of my head is a CMU block. Architects use that (concrete masonry unit) whereas laypeople call them “cinder blocks”.
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### Author:  [@kayaker](https://boards.straightdope.com/u/kayaker)
#### Post date: [September 1, 2015, 12:03pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/17 "2015-09-01T12:03:15Z")
Supplementary, complementary, alternative medicine to its proponents, while others just use the abbreviation.
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### Author:  [@Learjeff](https://boards.straightdope.com/u/Learjeff)
#### Post date: [September 1, 2015, 12:04pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/18 "2015-09-01T12:04:24Z")
> [@JWT\_Kottekoe](#):
>
> “growing exponentially”
How is that commonly misused?
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### Author:  [@Amateur\_Barbarian](https://boards.straightdope.com/u/Amateur_Barbarian)
#### Post date: [September 1, 2015, 2:09pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/19 "2015-09-01T14:09:40Z")
> [@TriPolar](#):
>
> Yeah, the whole switching mechanism is referred to as a solenoid often, but it’s still a switch that uses a solenoid.
It’s a little archaic, but I have references around here to a big switch that actuates heavy machinery through things like relays as… a solenoid. Perhaps a case of the function transferring to the function-ator.
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### Author:  [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)
#### Post date: [September 1, 2015, 2:53pm UTC](https://boards.straightdope.com/t/same-item-different-field-different-terms/729529/20 "2015-09-01T14:53:04Z")
Going back to the OP:
Historically, a solenoid was a simple short-throw linear motor. A contactor was a high power electrical switch, typically moved mechanically by a solenoid. A relay was a low-powered contactor which may have used an electromagnetic mechanism other than a solenoid.
The terms were clear and distinct in EE. Non technical workers out in the field have been colloquially misusing nearby terms as synonyms since the advent of the first hand axe.
Now of course we have “solid state relays” which preserve the gross idea of relay: “use one electrical circuit to switch another”, but lack the moving parts and don’t rely on electromagnetism for their working action.
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