The genitive case. The formation of the genitive
The apostrophe is added only to regular plural nouns (boys', soldiers') and to Greek names in -s of more than one syllable: Archimedes' [a:kimi:di:z] Law, Sophocles' tragedies, Euripides' plays. With other proper names ending in -s there is vacillation both in pronunciation and spelling, but most commonly the spelling is the apostrophe only while the pronunciation is [iz]. Thus, Burns' (or less commonly, Burns's) is pronounced [-ziz]. Cf. also Dickens' novels, Jones' house etc. where the pronunciation is [ziz]. With compounds, the inflection -'s is added to the final element: my brother-in-law's children, my brothers-in-law's children. The Use of the Genitive The genitive case is used to express a variety of ideas: possession, relationship, physical features and characteristics, non-physical qualities and measurements. The -'s genitive mainly occurs with animate nouns denoting personal names (Jane's brother, Mr Wilson's library, George Washington's statue), personal nouns (the student's answer, the girl's letter) and animals with personal gender characteristics mostly domestic, or those that are credited with some intelligence (the dog's tail, the cat's paw, the elephant's trunk).