# Meaning of velocity - mass noun vs countable noun

Dictionary entries like https://www.oxfordlearnersdictionaries.com/definition/english/velocity?q=velocity state that velocity can be a mass noun or a countable noun. What is the difference between the following sentences?

The body has additional vibration velocity.

vs.

The body has an additional vibration velocity.

• I don’t know what “vibration velocity” is — we’d need a definition of that before we can help you. – Dan Bron Feb 17 at 18:27
• It seems to me that "velocity" behaves like "speed". "What speed was the car doing?" - countable. "Speed is of the essence" - non-countable. – WS2 Feb 17 at 18:27
• @DanBron It is a type of velocity that oscillates in waves (it's basically sinusoidal). – ExOrbitant Feb 17 at 18:29
• @WS2 ok, makes sense. May I ask you for your understanding with respect to my examples, please? – ExOrbitant Feb 17 at 18:41
• @ExOrbitant The mere fact that both are singular, but the first does not employ an article, and the second one does suggests that they are non-countable and countable respectively. – WS2 Feb 17 at 19:08

Employment / acceptance of an indefinite article isn't a good test for a count usage.

'She has a working knowledge of Spanish'. 7 working knowledges?

Here, though, the second sentence means

'The body has, in addition, vibration[al] velocity.'

Just as a body may possess kinetic energy of translation, KE of rotation, and, in addition, KE of vibration, it will correspondingly have associated translational and rotational velocities, and one assumes what may be labelled a vibrational velocity. Though 'velocities' is commonly used hereabouts, the use of numerals before the word is rare.

Velocity is probably best regarded as non-count in say Velocity is a vector quantity indicating not only speed but also direction (though the plural form isn't outlandish).

The first sentence sounds strange, and probably defaults to The body has vibration velocity over and above [what has been specified].

• Always a pleasure to read your insightful contributions @Edwin! If you say, the body possess kinetic energy, hence it has kinetic energy, why can‘t one say the body possesses velocity, hence it has velocity? Both are physical properties. – ExOrbitant Feb 17 at 20:10
• We're really into metaphor here ('possess' in its primary, basic sense means 'own; have legal ownership of' rather than just 'have), and no one would say 'the body owns kinetic energy'. The overlap of these synonyms is idiosyncratic. Although 'possesses kinetic energy' rings a bell with me from my undergraduate days, 'possesses vibrational velocity' just sounds weird. Even though 'the car has a velocity of ...' is fine when in the right circles, 'the X has a vibrational velocity of' sounds off. Wouldn't the velocity of vibration be constantly changing anyway, never constant? – Edwin Ashworth Feb 18 at 11:14
• Yes, vibration velocity changes continuously. I agree with you that one would say that 'a car has a velocity of x km/h' or if one refers to a special velocity 'the velocity of y km/h leads to engine damage'. As @Greybeard indicated, can't I say 'body has velocity'? My original sentence is: 'The blade has additional and constantly changing vibration velocity between the times t1 and t2, which is ignored in Equation x'. I merely want to describe the fact that the blade has, in addition to velocity v, vibration velocity u(t) (I'm not referring to a specific one). – ExOrbitant Feb 18 at 11:59
• If you mean ''The blade has, in addition, [a] constantly changing vibration velocity between the times t1 and t2 ..." which I think you must, not if you want to be a good follower of Grice (and scientists should aim for clarity). "Additionally, he has pain in his right leg" means "He also has pain in his right leg" whereas "He has additional pain in his right leg" defaults to "He has pain y in his right leg, on top of the pain x in his right leg already mentioned/deducible." While the other reading is possible, the ambiguity would only be removed by context (and is easy to avoid anyway). – Edwin Ashworth Feb 18 at 12:17
• I guess I could also say 'vibration velocity is an additional velocity term of the blade' (following your logic) – ExOrbitant Feb 18 at 12:48

What is the difference between the following sentences? 1 The body has additional vibration velocity. vs. 2 The body has an additional vibration velocity.

1 The body has velocity. -> the body possesses the abstract attributes of speed and direction. Here, we are saying that the body possesses speed and direction “in general”

vs.

2 The body has a velocity. -> the body possesses an example of a certain speed and an example of a certain direction. We are being a little more specific - the figures for each are real.

If we return to “vibration velocity” in 1, this means “general velocity that is associated with general vibration”. It is an uncountable noun phrase (comprised of two nouns used uncountably), which is a subset of the uncountable noun “velocity”. .

2 In, “a vibration velocity”, vibration is an uncountable noun (as above, it acts adjectivally), but “velocity” is countable and the sentence is to be understood as “The body has an example of an certain velocity associated with vibration in general.

Now for “additional”: In 1, it means greater than that in other bodies. In 2, it means one more “vibration velocity” than in other bodies.

• Makes sense! Thank you:-) – ExOrbitant Feb 18 at 6:01
• In 'He has an assurance, however misguided, that he will be able to survive six weeks in the desert,' 'assurance' does not satisfy the test for count usage that CGEL gives ( acceptability of numeral insertion), in spite of the correct use of the indefinite article. – Edwin Ashworth Feb 18 at 13:43
• "He has an assurance" is equivocal. Has he received an assurance (countable) from each of two sources, or is he confident (uncountable)? He can certainly receive two assurances but cannot possess two assurances. Taking the uncountable version, "that he will be able to survive six weeks in the desert," has a partitive effect on the class of things that are "assurance" and refers us to the type of assurance that is required. If we take "an" to mean "an example of a" we can see that "an" is not acting as a number, as "one" would be. – Greybeard Feb 18 at 14:28