Grammar girl here. Have you ever looked at one of those gigantic gumball machines that holds thousands of gumballs?

And wondered why it's called a gumball machine instead of a gumballs machine?

Or why people who manage projects in the corporate world are called project managers instead of projects managers?

You may have figured it was just one of the peculiarities of English that the first noun in a compound noun has to be singular

But then what about singles bars systems analysts and the rewards cards that so many stores are forcing us to get these days?

Let's start with some vocabulary we'll need to talk about compound nouns. In a compound noun such as gumball

The second noun, ball, is called the head noun. The head noun tells you what kind of thing the whole compound is referring to.

A gumball is a kind of ball. The first noun, gum, which modifies the head noun, is called an attributive noun or a qualifying noun.

Linguists have been trying to figure out what's going on with singular and plural inside English compound nouns for at least 30 years.

It turns out that there are some discernible patterns and tendencies,

but unfortunately, they're subject to a lot of variation and exceptions,

which makes them practically useless if you're just trying to figure out whether to go with a singular or a plural.

We'll look at these tendencies and give our quick and dirty tip for dealing with attributive nouns.

David Kristall, a linguist who's written many books on English,

notes that when there's a meaning difference between a compound with a singular attributive noun and when with a plural,

people usually keep the plural.

It'll be more clear with an example. Here we go. If I talked about a reward card,

instead of a reward's card, that could sound like a card that was given to me as a reward.

I also found out that system analysis is a field of electrical engineering,

so it makes sense that the business related term systems analysis uses the plural noun systems to distinguish itself.

For yet another example, sale often refers to an event in which normal prices are reduced.

Sales, however, refers to all purchases that a store's customers make, whether during a special event sale or not.

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