All drug leaflets list possible side effects of using the drug. Whenever muscle or joint pain is a possible side effect, it is listed in the singular (both muscle and pain), when it is generalized such that no specific muscle or joint is concerned (in many cases it is impossible to predict which muscle or joint will hurt, if any).

So why is it in the singular? Why not "muscles pain" or "muscles pains", which (ostensibly) includes the possibility of several different muscles hurting as a result of the drug?

My mother tongue is Hebrew, and in Hebrew we do say it in the plural, i.e. "muscles pains", Hence the question (I'm not suggesting that Hebrew and English should work the same, just wondering about the English form).

  • 2
    Because “muscle” in “muscle pain” works as an adjective (noun adjunct), so it is not pluralized.
    – user 66974
    Jul 31, 2018 at 9:39
  • Pain is both countable and uncountable, but it is most often used as a mass noun: books.google.com/ngrams/… - Muscle pain originates in any of the muscles in the body. - medicinenet.com/muscle_pain_myalgia/symptoms.htm
    – user 66974
    Jul 31, 2018 at 9:51
  • It's not relevant whether pain is countable or uncountable: see the examples in my answer, where some of the head nouns are countable and some uncountable, and the countable ones can all be used in the plural.
    – Colin Fine
    Jul 31, 2018 at 10:13
  • First off, if the leaflet says "muscle/joint pain" it means "muscle or joint pain".
    – Hot Licks
    Jul 31, 2018 at 11:10
  • For the record, you should never use a backslash in English: you mean "muscle/joint pain" as some sort of less than perfectly clear but commonly used shorthand for "muscle and joint pain" or maybe "muscle or joint pain". The backslash has no place in English spelling; it is a creature of computer programming alone. The proper slash is formally a SOLIDUS character, which has a positive slope. The wrong one, the backslash, has a negative slope.
    – tchrist
    Jul 31, 2018 at 20:34

2 Answers 2


There is a strong tendency (not just in English) that when a noun is used as a modifier for another noun, it loses its inflection (whether for number, case or anything else).

So in English, when a noun stands first in a noun phrase it is usually in the singular. When it is not, this is usually because the singular is open to ambiguity.

So car salesman, window cleaner, mouse trap (or mousetrap), bird feeder, tree planting, road building all use the singular.

  • 2
    Thanks, that's very helpful. It's interesting to note that in the word 'salesman' (which is a noun in its own right, but had obviously emerged from the combination of 'sales' and 'man', and was probably a noun phrase before condensing into a single noun), sales is in the plural.
    – Don_S
    Jul 31, 2018 at 10:21
  • Nice observation, @Don_S, but historically inaccurate. The OED says it's from sale's (possessive) and man: it says to compare craftsman, tradesman; and I would add sportsman, linesman, headsman, bandsman, yachtsman. Some of these you could make a case for the object being logically plural, but for most of them, no.
    – Colin Fine
    Jul 31, 2018 at 12:15

What the statement in the leaflet refers to is a "term" for a "condition."

Side effects may include certain defined conditions having specific names.

A condition where the patient experiences a sensation of pain in any muscle or joint may be called "muscle/ joint pain." It is not the sensation of pain itself that is being mentioned here, it is the condition or state of the patient.

Common minor side effects of prescription drugs:

  • Diarrhea
  • Dizziness
  • Drowsiness
  • Fatigue
  • Heart issues (palpitations, irregular heartbeats)
  • Hives
  • Nausea and vomiting
  • Rash
  • Stomach upset

(src: Drugwatch)

  • This is not an answer to the question; in fact it completely ignores the question itself. -1.
    – Colin Fine
    Jul 31, 2018 at 12:16
  • @ColinFine Note the OP's comment.
    – Kris
    Jul 31, 2018 at 12:23
  • Which comment, @Kris?
    – Colin Fine
    Jul 31, 2018 at 12:52

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