So, only add only ' (apostrophe) if the ending "s" was added to make it plural.
| Singular | Plural | Singular Possessive |
Plural Possessive |
| [NOUN] | [NOUN] +s | [NOUN] +'s | [NOUN] +s' |
| apple | apples | apple's | apples' |
| Mark | Marks | Mark's | Marks' |
| Johnson | Johnsons | Johnson's | Johnsons' |
| [NOUN] {} {s ss sh ch x o} |
[NOUN] {} +es {s ss sh ch x o} |
[NOUN] {} +'s {s ss sh ch x o} |
[NOUN] {} +es' {s ss sh ch x o} |
| atlas | atlases | atlas's | atlases' |
| boss | bosses | boss's | bosses' |
| marsh | marshes | marsh's | marshes' |
| stitch | stitches | stitch's | stitches' |
| fox | foxes | fox's | foxes' |
| potato | potatoes | potato's | potatoes' |
| Jones | Joneses | Jones's | Jonses' |
| [NOUN] y | [NOUN] y→i +es | [NOUN] y +'s | [NOUN] y→i +es' |
| puppy | puppies | puppy's | puppies' |
| pinky | pinkies | pinky's | pinkies' |
| lady | ladies | lady's | ladies' |
| city | cities | city's | cities' |
| [NOUN] {} {ay ey oy uy} |
[NOUN] {} +s {ay ey oy uy} |
[NOUN] {} +'s {ay ey oy uy} |
[NOUN] {} +s' {ay ey oy uy} |
| bay | bays | bay's | bays' |
| key | keys | key's | keys' |
| boy | boys | boy's | boys' |
| guy | guys | guy's | guys' |
| [NOUN] f(e) | [NOUN] f(e)→ve +s | [NOUN] f(e) +'s | [NOUN] f(e)→ve+s' |
| wolf | wolves | wolf's | wolves' |
| loaf | loaves | loaf's | loaves' |
| knife | knives | knife's | knives' |
| life | lives | life's | lives' |
| [NOUN] (irregular) |
[NOUN] (irregular) |
[NOUN]+'s (irregular) |
[NOUN]+'s (irregular) |
| child | children | child's | children's |
| mouse | mice | mouse's | mice's |
| person | people | person's | people's |
| a people | many peoples | a people's | many peoples' |
| money | monies moneys (pre 1970) |
money's | monies' moneys' (pre 1970) |
| it | they | its (no apostrophe) |
their |