Possessive Case

Forming a possessive case noun... It sometimes makes more sense to see the 's as a particle (or clitic) and not a case form. It may be somewhat analogous to the Afrikaans particle se. See brother-in-law's and Mark, Luke, and John's car below. Also, don't forget the example of I saw the King of Denmark's crown but I saw the Kings of Denmark's crowns.

Possessives notes:

• You add 's generally speaking for the singular possessive: the dog's leg
• You add ' for a plural possessor ending in -s (the tourists' luggage). This is true even if the plural is irregular: dwarves' noses
• If you have an irregular plural possessor that doesn't end in s, you use 's: children's playground. Generally, form the nominative plural first, and then figure out if you need an ' or an 's!
• Here is where 's as particle really makes sense. If several people own one thing, then there is a 's at the end of the series: Mark, Luke, and John's car. But if they each have a car it's: Mark's, Luke's, and John's cars.
• Add 's to proper nouns even if they already end in an s. This is always acceptable, but some styles allow some variation on this: Dickens's book
• The possessive of a proper plural noun is regular: the Smiths' house. A variation of this is often seen on signs and mailboxes: The Smiths'. But I'm not sure to what the possession refers. Is it their mailbox, address, house? Maybe not using the apostrophe is actually acceptable or even the "official" way of doing this, but everyone uses an apostrophe anyway. This is completely confused with making a simple plural (non-possessive) form of a family name: The Frankses have..., not The Franks' have.... But note here that there is a difference between how proper noun plurals are formed compared to normal plurals: Murphy/Murphys
• The possessive plural of proper names is formed by just adding a ' regardless of whether it ends in an s or not. Form the plural first(!): The Smiths', The Dickenses'
• Note that to form a plural (not possessive) of abbreviations or numbers, you don't use an apostrophe usually: IRAs, PhDs, 1960s. (But note plural possessive the 1960s' greatest hits.) The idea here is that capital letters and numbers are distinct enough that an apostrophe just isn't needed. But the plural of letters do take 's: Mind your p's and q's, two B's on a report card . I guess ps and qs just isn't distinct enough. The Chicago Manual of Style and the MLA Handbook do not agree here.

My Handy Table with Examples

	Possession in English
	Normal Nouns
Nom. Sing.	dog
Poss. Sing.	dog's
Nom. Plur.	dogs
Poss. Plur.	dogs'
	Nouns in an s-sound (also z-, č-, š-, or (d)ž-sound)
Nom. Sing	match
Poss. Sing.	match's
Nom. Plur.	matches
Poss. Plur.	matches'
	Nouns with an irregular plural not in an s-sound
Nom. Sing.	ox, deer
Poss. Sing.	ox's, deer's
Nom. Plur.	oxen, deer
Poss. Plur.	oxen's, deer's
	Nouns with an irregular plural in an s-sound
Nom. Sing.	dwarf
Poss. Sing.	dwarf's
Nom. Sing.	dwarves
Poss. Plur.	dwarves'
	Family Names
Nom. Sing.	Smith, Franks, Murphy
Poss. Sing.	Smith's, Franks's, Murphy's
Nom. Plur.	Smiths, Frankses, Murphys
Poss. Plur.	Smiths', Frankses', Murphys'
	Family Names in Silent -s, -x, or -z Authorities disagree.
Nom. Sing.	Margaux, Descartes, Dumas
Poss. Sing.	Margaux'(s), Descartes'(s), Dumas'(s)
Nom. Plur.	Margaux, Descartes, Dumas
Poss. Plur.	?Margaux's, ?Descartes's, ?Dumas's
	Abbreviations and Numbers Chicago has PhDs and Ph.D.'s
Nom. Sing	IRA, PhD, Ph.D.
Poss. Sing.	IRA's, PhD's, Ph.D.'s
Nom. Plur.	IRAs, PhDs, Ph.D.'s, 1960s
Poss. Plur.	IRAs', PhDs', ?Ph.D.s', 1960s'
	Letters
Nom. Sing.	q
Poss. Sing.	q's
Nom. Sing.	q's
Poss. Plur.	?qs'
	Latin (and Greek)
Nom. sing.	alumnus, alumna, medium, index
Poss. Sing.	alumnus's, alumna's, medium's, index's
Nom. Plur.	alumni, alumnae, media, indices
Poss. Plur.	alumni's, alumnae's, media's, indices'
	Italian
Nom. Sing.	soprano
Poss. Sing.	soprano's
Nom. Plur.	soprani
Poss. Plur.	soprani's
	For Euphony's Sake (An 's in the poss. sing. is always acceptable here according to MLA. Chicago disagrees. Also, polysyllabic Greeks in -s are here.)
Nom. Sing.	appearance, Jesus, Xerxes
Poss. Sing.	appearance'(s), Jesus'(s), Xerxes'(s)
Nom. Plur.	appearances
Poss. Plur.	appearances'
	Compound Nouns The possessive plurals are usually not used. The sentence is reworded.
Nom. Sing.	attorney general, brother-in-law, woman doctor
Poss. Sing.	attorney general's, brother-in-law's, ?woman doctor's
Nom. Plur.	attorneys general, brothers-in-law, women doctors
Poss. Plur.	attorneys general's, brothers-in-law's, ?women doctors'
	Already Has an Apostrophe
Nom. Sing.	McDonald's
Poss. Sing.	McDonald's
	What To Do Here? Barclays and St Andrews no longer officially have an appostrophe.
Nom. Sing.	Barclays, St Andrews
Poss. Sing.	?Barclays's, ?St Andrews's
	Pronouns
Nom. Sing.	one, everyone, it
Poss. Sing.	one's, everyone's, its