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I'm an engineer and I often hear others say "the motor speed" when they are talking about the speed of the motor. For example, one might ask "What was the motor speed?" when he or she wants to know what the speed of the motor was. I've seen similar phrases in scientific journals too. Why is it OK to say "the motor speed" when you are talking about the speed of the motor?

Mari-Lou A
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Engineer
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    Can you explain why it wouldn't be okay? Do you have the same problem with "internet speed"? – Gob Ties Mar 27 '14 at 19:02
  • @Geobits I think the OP may be wondering why we don't say 'the motor's speed'. – WS2 Mar 27 '14 at 19:11
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    This question is a better fit for ELL. It appears that you are asking about the simple use of an adjective. In motor speed, motor in an adjective, just like it is in motor oil. – Canis Lupus Mar 28 '14 at 02:55
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    @WS2 I believe the OP is asking why we place the noun, motor, immediately before another noun, in this case, speed, and we understand it to mean the the speed of the motor. Similar noun adjuncts are a book cover (the cover of a book), a rope bridge (a bridge made of rope), matchbox (a box for matches), a four star hotel (a hotel with four stars) etc. – Mari-Lou A Mar 28 '14 at 07:48
  • possible duplicate of Using apostrophes correctly I believe this question may be of valid help. If it isn't, please say so and I will delete my request to close your question as being a duplicate. – Mari-Lou A Mar 28 '14 at 07:48
  • related http://english.stackexchange.com/questions/87609/is-this-noun-used-as-an-adjective and http://english.stackexchange.com/questions/87591/a-noun-adjunct-the-possessive-case – Mari-Lou A Mar 28 '14 at 07:58
  • Ciao Mari -- you know, I don't think this question is a duplicate at all. – Fattie Mar 28 '14 at 13:16
  • @JoeBlow the question isn't a duplicate, but I did say it could help, plus the other questions are all related as to whether we should use apostrophes or just the bare noun. I looked quite extensively, but there doesn't seem to be a canonical answer in EL&U It is as WS2 said, you have to memorise noun adjuncts/compound nouns and get a feel for when to say/add an "s" and when to use the possessive apostrophe in writing. – Mari-Lou A Mar 28 '14 at 21:22

3 Answers3

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If you are wondering why we don't say 'the motor's speed', it is just that idiomatically, with very specific things we simply drop the apostrophe s.

Doctor's and nurses will talk about their patients' 'heart rate', 'pulse rate', 'breathing rate', 'blood count', 'flesh tone'. We talk about having 'kidney trouble', or 'liver trouble'.

When driving a car we will watch out for the 'speedometer reading'. We replace faulty 'headlight bulbs' etc.

In the garden we will use a 'hedge trimmer', 'garden shears' etc.

In none of these examples and scores more, where you might expect to find a possessive apostrophe, they are dropped and a 'compound noun' is formed. Some people might argue that such terms should be hyphenated.

WS2
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  • How will I know when it is OK to do this? For example, if I'm talking about the age of the universe can I say "the universe age"? – Engineer Mar 27 '14 at 19:40
  • @Engineer No I'm afraid you can't say 'the universe age'. It has to be something that is used so frequently that a 'compound noun' has been established. I cannot think of a rule, other than simply learning by listening and experience. I don't know if anyone else can. You may find a good dictionary helpful. – WS2 Mar 27 '14 at 20:21
  • WS2, you can certainly say "Universe age" in certain contexts - I've used that, funnily enough. No problem at all. (In a context much like "motor speed," we were discussing something like "system age" "ship age" and ultimately "universe age".) – Fattie Mar 28 '14 at 10:37
  • "In English, you can use a noun as an adjective." Table age, plastic age, motor speed, TGV speed, light speed, dog years, cat years, internet posts, snail speed, internet speed, USA time, Superhero speed, America speed, Europe speed, racehorse speed, ice age, snail age, internet age, etc etc – Fattie Mar 28 '14 at 10:44
  • @JoeBlow Can you answer the OP's question, namely 'How will I know when it is OK to do this?' – WS2 Mar 28 '14 at 11:21
  • {You know, I just realised physicists use "universe age" as a matter of course. Assume a universe age of 5by, a new paper on the universe age problem, universe age is unknown in this paper, etc.} – Fattie Mar 28 '14 at 12:00
  • 'How will I know when it is OK to do this?' You can always do it. Nouns can be adjectives in English. I can't think of a counter example (or even a pansyass example) where it doesn't work. I can't think of anyway at all to label, or describe, "motor speed" other than "motor speed". – Fattie Mar 28 '14 at 12:08
  • @JoeBlow But if you wanted to say 'the front door of my house is locked', you wouldn't say 'my house front-door is locked', would you? Wouldn't you say 'my house's front-door is locked', or 'the front-door of my house is locked'? Or 'my dog's tail is long'? You couldn't say 'my dog tail is long' - that would suggest it was something attached to you. – WS2 Mar 28 '14 at 12:48
  • Let's think ... "my house door is locked" is completely common. Regarding dog tail, funnily enough I was in Derolle recently and we said things like "that dog tail is long, but that cheetah tail is short". Couldn't be more normal. By all means, when you're referring to my dog's dog tail, you would probably say "my dog's tail is long". (But so what? For "motor speed" I can give 1000 examples where you would probably say "speed of the motor" or some other combination.) If you commonly worked with dog tails (you're a vet or taxidermist), you might occasionally refer to .... – Fattie Mar 28 '14 at 12:54
  • ... to your own dog's tail as "Fido's dog tail" (of course, you could just say "Fido's tail" also). It would be totally commonplace that engineers occasionally say "what is the motor's motor speed?" "Check motor seven's motor speed." And so on. (Also, TBC, "my house front-door is locked" I say that all the time, as well as "my house door is locked".) By the way, you'll love this. You know what engineers that design engines (eg, at BMW) are called? Engine engineers! Heh! – Fattie Mar 28 '14 at 12:57
  • (Dog tail -> dog tale -> shaggy dog story ... heh!) – Fattie Mar 28 '14 at 13:00
  • (For millions of "house door" references, any hardware or building. Also barn door, stage door, storm door, trap door, etc etc ...) – Fattie Mar 28 '14 at 13:02
  • @JoeBlow Now all we need to do is to summarise those four posts of yours into a rule, and state it for the benefit of the non-native OP, so that he will instantly know when he can say 'dog tail' and when he has to say 'dog's tail'. – WS2 Mar 28 '14 at 13:26
  • Sure - adjective-noun is for a type of thing. apostrophe-s is for possession. – Fattie Mar 28 '14 at 13:56
  • Does “the motor speed” mean the speed of the motor? Answer: absolutely not. "motor speed" is a type of speed. But when you say "the" motor, you are referring to some specific motor. (Say, "Motor X11".) Note that MotorX11 will indeed have a motor speed. But as a matter of fact, MotorX11 will indeed also have a air speed. And - you guessed it - MotorX11 will indeed also have a linear speed, and a fuel speed, and a decay speed, and a banking speed, and an angular speed, and a vertical speed. It just couldn't be simpler. – Fattie Mar 28 '14 at 14:05
  • @Joe Blow 'Sure - adjective-noun is for a type of thing. apostrophe-s is for possession.' But 'my dog's tail' is a 'type of thing' - why can't I say 'my dog tail'? – WS2 Mar 28 '14 at 14:10
  • Note that if an engine engineer points at an engine and commands "Tell me the color". Of course - obviously - he means "tell me the color of the thing I'm pointing at." The sentence fragment "tell me the color" is completely meaningless, unless you are pointing at an object. Similarly, the sentence fragment "Tell me the motor speed", is utterly meaningless. – Fattie Mar 28 '14 at 14:15
  • why can't I say 'my dog tail'? Are you kidding at this point? YOU CAN, ABSOLUTELY say "my dog tail". I have said it. (Amazingly, I gave you AN ACTUAL EXAMPLE of me saying it, at a taxidermists, recently. What more do you want?). "dog tail" is A TYPE OF THING (a type of tail). You can and should use the double word "dog tail", any time you are referring to, the type of tail we call "dog tail". You can use "the dog's tail" or "Fido's tail" -- as you must know -- in the usual way possessive apostrophe-S is used: to mean a tail owned by "Fido" or owned by "the dog". – Fattie Mar 28 '14 at 14:18
  • Regarding the OP's example. If his boss POINTS AT a specific motor and says "tell me the motor speed" -- obviously, surely anyone would understand this -- that is equivalent to saying "Tell me the motor speed of that motor". Very simply, you CAN NOT say the word collection: "tell me the motor speed". It is as completely meaningless as "tell me the color". – Fattie Mar 28 '14 at 14:21
  • "why can't I say 'my dog tail'?" You CAN NOT say "dog tail" to REFER TO your dog Fido's tail. "dog tail" means a type of tail. To REFER TO your dog Fido's tail you have to say "Fido's tail" or "the dog's tail". However, you can certainly say "Fido's tail is a dog tail." After medical experimentation, it would be perfectly normal to say "Fido's tail is now a wolf tail" or "Fido's tail is now a cat tail." – Fattie Mar 28 '14 at 14:28
  • Note that you wrote: "But 'my dog's tail' is a 'type of thing'". That is totally incorrect. (Unless you're just being funny, as in: "hey, my dog's tail 'is' meat, why can't I use that word, meat!") The referent of "my dog's tail" is: a tail belonging to your-dog. It's that simple. The referent of "dog tail" is: a certain type of object. – Fattie Mar 28 '14 at 14:33
  • @JoeBlow I don't dispute much of what you say. But I am not sure you have explained to a non-native speaker when they can omit an apostrophe. Let's say my friend and his wife travel in my car, and next day I notice a lady's coat on the back seat. Can I phone my friend and say 'you left your wife-coat in the car'? But I could say 'I found it on my car-seat'. (I probably wouldn't, but you may see my point). What is the difference between these two examples? Why a 'car seat' but not a 'lady coat'? – WS2 Mar 28 '14 at 15:40
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"Motor speed" is likely used as a contrast to "land speed", "air speed", etc. A motor speed would likely be measured, for example, in RPM, whereas other relevant speeds could be measured in MPH, or some other measure.

For example, in a motor boat, the motor speed is not necessarily proportional to the "actual" speed of the boat (when accelerating, for example, there's some delay between throttling up and actual acceleration).

calvin
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    'Motor speed' is a totally different concept to 'land speed', or 'air speed'. 'Motor speed' is that at which the motor is running. But the others are not the speed at which the land or the air are moving. 'Land speed' is that at which the vehicle is moving over land, and similarly through the air. I feel you have answered the OP as if he had posed an engineering question. But the fact that it is raised on a language site tells me he is wondering why there is no apostrophe s. – WS2 Mar 27 '14 at 19:38
  • Right. The OP is asking how noun adjuncts work in English. – Fattie Mar 28 '14 at 10:38
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It's amazing someone hasn't simply answered:

"it's an adjective."

High speed, slow speed, stalling speed, motor speed.

This couldn't be simpler...

.

one is a "type of thing" (eg, "aircraft door")

the other is possession (eg "John's door")

Full, total explanation...

https://english.stackexchange.com/a/160389/8286

Full line-by-line explanation of this question:

.

I'm an engineer and I often hear others say "the motor speed" when they are talking about the speed of the motor.

Wrong. They are talking about the "motor speed" of a specific motor, say TestMotor1234.

For example, one might ask "What was the motor speed?" when he or she wants to know what the speed of the motor was.

Wrong. They are asking "What was the motor speed of TestMotor1234?"

I've seen similar phrases in scientific journals too.

You have not. Sentences need an object.

Why is it OK to say "the motor speed" when you are talking about the speed of the motor?

Why would it not be? "What is the motor speed of TestMotor1234?"

Note that if you physically point at an object and say "What's the color?" that is - of course - the same as saying "What is the color of that object?"

The sentence fragment, on its own "What is the color", is utterly meaningless.

The sentence fragment, on its own "What is the motor speed", is utterly meaningless.

Community
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Fattie
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  • Forget about motor speeds for a minute. When does a 'possession' become a 'type of thing', as you describe them? We both agree things like 'barn door, car seat, house paint, tea bag, animal feed, dog tooth, coffee mug etc' don't need apostrophe s. But what about 'men's underwear, lady's shoes,child's necklace, cow's milk, doctor's stethoscope, lawyer's office, etc' - why do they all need apostrophe s? That is what the OP is asking. How can he know when to omit the apostrophe? – WS2 Mar 28 '14 at 15:56
  • "cow milk" "child necklace" etc are perfectly common. when you say "we both agree.." that's wrong. when you say "all need" that's also wrong. when you try to conflate away the difference between a type-of-thing and someone's thing, that's wrong! you're pointing out that you can also (in some cases) use apostrophe-s to refer to a type-of-thing. But so what? Simply re-read the "Full line-by-line explanation of this question:" for full details! no need to copy and paste it here – Fattie Mar 29 '14 at 06:55
  • I see the point that Joe Blow is making. However, one would say "the speed of TestMotor1234" and not "the motor speed of TestMotor1234". Speed by itself would be understood as the rotational speed of the shaft. I think the problem might be that I don't understand when the apostrophe s can be left out just as WS2 and Mari-Lou A pointed out. Although, "motor's speed" sounds a bit off too in my opinion. In my native language there exists a similar feature to the apostrophe s and you could not leave it out in this case but in some other cases you could. This is what is confusing me I think. –  Mar 28 '14 at 18:37
  • A winter coat (a coat for the winter), a raincoat (an impermeable coat / a coat to keep you dry), but we say "a boy's coat" and "women's clothes". The first two compounds describe the type of coat, its use; whereas a child's coat doesn't tell us its function but its owner, and if you visit a department, you'll know that the floor sells clothes made for women (the future owners). Likewise, the dog's tail tells us who the owner is, while the motor speed describes what type of speed, but not its owner. This explanation is greatly simplified, but it should work in many cases. – Mari-Lou A Mar 28 '14 at 21:14
  • @Mari-LouA we also say 'cow's milk, a doctor's coat, lawyer's office, men's shoes', and thousands more, yet 'dog basket, water heater, car tyre' etc. There seems no rhyme nor reason as to which one is used. – WS2 Mar 29 '14 at 06:21
  • @Mari-Lou A I don't think that "the motor speed" describes what type of speed. It is just that the "'s" or the "of the" have been left out for some reason. For example, one might say something like "Motor 1 speed is good but Motor 2 speed is too low". The type of speed is the same with Motor 1 and Motor 2, i.e., rotational speed of the shaft. Another example is "the speedometer reading" as WS2 pointed out. If I'm in a car with a friend and I say "the speedometer reading" I'm referring to the reading of the speedometer on the dashboard. –  Mar 29 '14 at 10:31
  • @WS2 Both "cow's milk" and "cow milk" are acceptable, it depends on the context. Parmesan cheese, for example, is made from cow's milk whereas pecorino is made from sheep's milk. But the milk I buy at the supermarket is cow milk. A doctor's coat does not tell us its function, but rather who the owner is, likewise men's shoes tell us to whom the shoes are sold. A dog basket, tells us what type of basket it is, presumably a cat basket is different (I don't have pets), but the dog's basket looks a bit grubby and needs changing is perfectly acceptable. – Mari-Lou A Mar 29 '14 at 12:41
  • I'm not implying my reasoning fits 100% of the time, it doesn't, there will always be exceptions, but for a learner it's not a bad rule to begin with. – Mari-Lou A Mar 29 '14 at 12:44
  • @Mari-LouA Well I've never said 'cow milk' in my life, and can never recall it being said. What about a 'doctor's stethoscope', 'bricklayer's pallet', 'electrician's screwdriver', 'farmer's boots', butcher's apron etc? – WS2 Mar 29 '14 at 12:56
  • @WS2 What about them? I'd place all those items you mentioned, in the same category as women's clothes and men's shoes. Do we say kitchen's floor? Not usually, because we don't think of the kitchen as owning the floor. Do we say knee's pads or knee pads, bedroom's curtains or bedroom curtains? Usually we say the latter. – Mari-Lou A Mar 29 '14 at 13:12
  • @Mari-LouA Yes, my point all along has been that there are these two forms. But can we state succinctly in a couple of sentences a rule for which ones require the possessive? That, incidentally, is what I managed to gather from the OP was what he wanted to know. – WS2 Mar 29 '14 at 13:21
  • @WS2 perhaps "a rule of thumb", rather then a couple of sentences which explain fully and concisely the use of the possessive versus compound nouns. At least I tried to give a rough outline. And by all means, why don't you try!? :) – Mari-Lou A Mar 29 '14 at 13:33
  • @Mari-LouA Before you got involved in this argument a bloke called Joe Blow kept telling me that the whole thing was obvious - one was possessive, the other a 'type of thing' Try as I might I couldn't get him to state what the difference was between the two. My argument all along has been that there is no rhyme nor reason. It is like so many English county boundaries, they just meander drunkenly across the countryside, and you are never sure what falls on one side and what on t'other. – WS2 Mar 29 '14 at 14:34
  • @WS2 I have come across this question, and the top answer handles very well the conundrum between choosing the possessive -s and of construction http://english.stackexchange.com/a/30402/44619 The examples Cerberus/Burchfield gives made me gawp and say aloud:Oh yeah, you're right! – Mari-Lou A Mar 29 '14 at 21:47
  • @Mari-LouA Yes, that seems to deal with that aspect very well. – WS2 Mar 29 '14 at 21:59
  • @Mari-Lou A But when is it okay to omit the possessive construction altogether? For example, is it okay to say "The circle radius is 100 cm." if what you mean is "The radius of the circle is 100 cm." or "The circle's radius is 100 cm."? –  Mar 30 '14 at 10:47
  • @Engineer I have provided you with a plethora of links, I have also attempted to give a rule of thumb rule, have you read them? If you are still confused, then may I suggest that you write a new question. :) – Mari-Lou A Mar 30 '14 at 10:53
  • Well I've looked through all of the posts and links and so far I've got two possible answers. The first one is that "motor speed" is a type of speed. I don't think that is the case as it would be silly to say "the motor speed of the motor" or "the motor's motor speed". The second one is that there is no way of knowing whether the possessive construction can be left out or not except based on experience. I guess the second one will have to do then. Thanks! –  Mar 30 '14 at 12:44