The plural of 'passerby' is 'passersby' with an 's' acting like an infix (W-B says that this is the only plural form of the word). This seems like a very interesting exception, so I thought I would ask a question.

Are there any other English words that are made plural by an 's' put inside the noun?

One criterion has to be met: the singular noun is composed of one (unhyphenated) word only.


It's a classic example of a compound noun where the noun is first. In compound nouns the head is often pluralized. Generally compound word plurals are often arbitrary. Yay!

Have a look at this blog from Cambridge




The table of changing plurals over here suggests that the 's' tends to move to the end over time. It lists the same bucketsful Lawrence mentions in the comments with the new style plural bucketfuls.

EDIT: Dang, you can't just make up more rules ;) But Sister-in-law holds up.

| improve this answer | |
  • The number of rules has diminished by one, but the question has turned out to be a duplicate. Thank you for your time and have a good one :) – Michael Smith Aug 6 '16 at 8:08

Not the answer you're looking for? Browse other questions tagged or ask your own question.