Have you subscribed to The Write Fit?

Compound nouns and plurals

Posted by Wendy Wood on 22nd September , 2020 in Grammar
Share this

I was thinking of my brother’s wife and my husband’s sister today. Each one separately is my sister-in-law, right? But, what do I call them when I want to refer to the two of them together?

Sister-in-law is a compound noun. A compound noun is just a fancy way of saying you’re using two or more words joined together to describe a person, place or thing. Many compound nouns are written as one word — for example, bathroom, doorjamb, and baseball. Others, such as bottle opener, dog food and car park, are written as two words. Still others are written with hyphens, which brings us back to sister-in-law.

The trick for making a hyphenated compound noun plural is to determine the main noun and then add an s to it. What’s the main noun in sister-in-law? Sister. Law simply tells you what kind of sister she is. So, you can invite your two sisters-in-law to a party, or you could have a meeting with two editors-in-chief. If you tied for second place in a writing contest, you’d be one of the runners-up.

My rule for compound words is to always look them up. A good dictionary will tell you the proper form for a compound noun and its plural.

Wendy Wood


Did you enjoy Super Grammar?

Get a new and super useful grammar tip from our proofreader Wendy, directly to your inbox, once a fortnight in Typeset’s The Write Fit newsletter. Subscribe here:



Know what you need?
Get in touch for an obligation-free chat!

Let's get started

© 2024 Typeset®. All rights reserved. Work With Us

I’d like free content marketing insights
Pop your email in the box and we’ll keep in touch through our newsletter, which is jam-packed with great information and advice. (We’ll never pass on your details to anyone!)

Site by StudioJS