Compound nouns form their plural by adding -s to the principal word:
In compounds with man/woman both words are pluralise:
|man fiend||man friends|
|woman doctor||women doctors|
Compounds ending in -man , change -man into -men in the plural. There is only a slight difference or none in the pronunciation.
Compounds ending in the -ful form their plural by adding -s:
Compounds containing no noun, form their plural by adding -s to the last word.