Compound nouns can be tricky because their plural forms don’t always follow simple rules. The table below lists common compound nouns with their singular and plural forms side by side for easy reference.
| Singular | Plural |
|---|---|
| mother-in-law | mothers-in-law |
| father-in-law | fathers-in-law |
| brother-in-law | brothers-in-law |
| sister-in-law | sisters-in-law |
| son-in-law | sons-in-law |
| daughter-in-law | daughters-in-law |
| editor-in-chief | editors-in-chief |
| commander-in-chief | commanders-in-chief |
| runner-up | runners-up |
| hanger-on | hangers-on |
| looker-on | lookers-on |
| passerby (or passer-by) | passersby (or passers-by) |
| attorney general | attorneys general |
| court-martial | courts-martial |
| sergeant major | sergeants major |
| governor-general | governors-general |
| notary public | notaries public |
| poet laureate | poets laureate / poet laureates |
| aide-de-camp | aides-de-camp |
| lady-in-waiting | ladies-in-waiting |
| lord-in-waiting | lords-in-waiting |
| man-of-war | men-of-war |
| man-at-arms | men-at-arms |
| man of letters | men of letters |
| chief of staff | chiefs of staff |
| work of art | works of art |
| coat of arms | coats of arms |
| bill of fare | bills of fare |
| mother-to-be | mothers-to-be |
| check-in (noun) | check-ins |
| check-out (noun) | check-outs / checkouts |
| check-up (noun) | check-ups |
| go-between | go-betweens |
| grown-up (noun) | grown-ups |
| good-for-nothing (noun) | good-for-nothings |
| no-hitter | no-hitters |
| merry-go-round | merry-go-rounds |
| jack-in-the-box | jack-in-the-boxes |
| forget-me-not | forget-me-nots |
| runner-on | runners-on |
| passer-on | passers-on |
| breakthrough | breakthroughs |
| trade-off | trade-offs |
| follow-up (noun) | follow-ups |
| take-off (noun) | take-offs |
| standby (noun) | standbys |
| standout (noun) | standouts |
| lookout (noun) | lookouts |
| takeaway (noun) | takeaways |
| setup (noun) | setups |
| login (noun) | logins |
| dropout (noun) | dropouts |
| carry-over (noun) | carry-overs |
| leftover (noun) | leftovers |
| passer-through (rare) | passers-through |
| spoonful | spoonfuls (spoonsful is rare) |
| cupful | cupfuls / cupsful |
| handful | handfuls |
| armful | armfuls |
| mouthful | mouthfuls |
| basketful | basketfuls |
| bucketful | bucketfuls |
| glassful | glassfuls |
| plateful | platefuls |
| aircraft | aircraft |
| spacecraft | spacecraft |
| hovercraft | hovercraft |
| watercraft | watercraft |
| means (singular or plural) | means |
| species | species |
| headquarters | headquarters |
| crossroads | crossroads |
| brainchild | brainchildren |
| passer-by (hyphenated form) | passers-by |
| court of appeal | courts of appeal |
| letter carrier | letter carriers |
| truck driver | truck drivers |
| piano tuner | piano tuners |
| washing machine | washing machines |
| credit card | credit cards |
| bank account | bank accounts |
| timekeeper | timekeepers |
| greenhouse | greenhouses |
| toothbrush | toothbrushes |
| bedroom | bedrooms |
| seafood | seafoods (uncountable in many contexts) |
| sunlight | — (uncountable) |
| snowfall | snowfalls |
| rainfall | rainfalls |
| football | footballs |
| wallpaper | wallpapers |
| smartwatch | smartwatches |
| schoolboy | schoolboys |
| schoolgirl | schoolgirls |
| housewife | housewives |
| fisherman | fishermen |
| fireman | firemen |
| postman | postmen |
| policeman | policemen |
| policewoman | policewomen |
| workman | workmen |
| spokesman | spokesmen |
| spokeswoman | spokeswomen |
| chairperson | chairpersons / chairpeople |
| stepbrother | stepbrothers |
| stepsister | stepsisters |
| stepchild | stepchildren |
| step-son | stepsons |
| step-daughter | stepdaughters |
| step-father | stepfathers |
| step-mother | stepmothers |
| boyfriend | boyfriends |
| girlfriend | girlfriends |
| sister-state | sister-states |
| city-state | city-states |
| attorney-at-law | attorneys-at-law |
| editor-at-large | editors-at-large |
| passer-out (BrE, rare) | passers-out |
| soldier of fortune | soldiers of fortune |
| man-hours | man-hours |
| woman doctor | women doctors |
| child prodigy | child prodigies |
| court reporter | court reporters |
| car park | car parks |
| dining room | dining rooms |
| coffee table | coffee tables |
| data point | data points |
| user-friendly (as noun “a user-friendly”) | user-friendlies |
| drive-through (noun) | drive-throughs |
| push-up (exercise) | push-ups |
| sit-up (exercise) | sit-ups |
| get-together (noun) | get-togethers |
| add-on (noun) | add-ons |
| spin-off (noun) | spin-offs |
| one-off (noun) | one-offs |
| passer-off (rare) | passers-off |
| intake (noun) | intakes |
| outbreak | outbreaks |
| afterthought | afterthoughts |
| overthrow (noun) | overthrows |
| underpass | underpasses |
| passer gate | passer gates |
| snowman | snowmen |
| English-speaker | English-speakers |
| French-speaker | French-speakers |
| passer rating | passer ratings |
| life jacket | life jackets |
| safety pin | safety pins |
| fire extinguisher | fire extinguishers |
| water bottle | water bottles |
| bottle opener | bottle openers |
| haircut | haircuts |
| takeaway pizza | takeaway pizzas |
| video game | video games |
| power plant | power plants |
| solar panel | solar panels |
| wind farm | wind farms |
| child-care worker | child-care workers |
| stay-at-home (noun) | stay-at-homes |
| never-do-well | never-do-wells |
| wannabe (noun) | wannabes |
| has-been (noun) | has-beens |
| also-ran (noun) | also-rans |
| passer-over (rare) | passers-over |
| passer-under (rare) | passers-under |
| man-servant | men-servants |
| maid-servant | maid-servants |
