English for Today by Ganiu Abisoye Bamgbose (Dr GAB)
PLURALISING COMPOUND NOUNS
That’s not expected of ~grownsup~ (nonstandard).
That’s not expected of *grownups* (standard).
If you say that someone is a grownup, you mean that they are an adult or that they behave in a responsible way.
I had some ~Boys Scout~ as friends (nonstandard).
I had some *Boy Scouts* as friends (standard).
Note that the initial letters are written in capital form.
I know a number of ~deafs-mute~ (nonstandard).
I know a number of *deaf-mutes* (standard).
A deaf-mute is a person who can neither hear nor speak.
GAB
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