So I was taught that you should almost always use singular form of an adjective instead of plural form. But recently, I've seen people using plural form and it sounds quite weird and I don't know if it is correct.
For example,
- "Salary tax" instead of "Salaries tax"
- "Office supplies" instead of "Offices supplies"
- "Product demo" instead of "Product demo"
In the above cases, the word "Salary" is used as an adjective to describe the type of "tax", so it will be in singular form. But I saw people using salaries tax and not sure if it is grammatical.
So my question is if there are any general rules on how to use the singular/plural form of an adjective?
Best Answer
As snailplane and Man_From_India tell you, your question does not involve adjectives, which never have a distinct plural form, but attributive nouns.
The singular form is certainly the ‘default’ for attributive constructions, but plural attributives are not uncommon. Some of these (and probably most of the older ones) come about because the singular and plural forms have different meanings. For instance
In other cases, the plural seems to have come about as a sort of compromise where the underlying sense might represent a simple plural or a singular possessive or a plural possessive—see, for instance, this blogpost on the correct spelling of Veterans Day. (But this is by no means a rule; see this Google Ngram on various names for the laws under which US workers are compensated for on-the-job injuries.)
In yet other cases, grammatical concord seems to be in play. We speak of Virginia Woolf as a woman writer, but we are more likely to call Woolf and Eudora Welty and Flannery O’Connor women writers than woman writers. Geoffrey Leech, in Change in Contemporary English, Cambridge, 2009 (220) suggests that this is more likely when the plural is irregular, without an -s.
But none of this explains why plural attributives became much more common in the second half of the 20th century, particularly in British English. Leech suggests that:
Leech says that Stig Johannson, Plural attributive nouns in present day English, Univ. Lund, 1980, identifies more factors, but this does not appear to be available free online.