sześciu

In a sentence

• Mam sześciu braci.

  I have six brothers.

  Here, 'sześciu' is the genitive masculine personal numeral used to describe the number of masculine personal nouns, in this case 'brothers'.

• Porozmawiajmy o sześciu sprawach.

  Let's talk about six matters.

  In this instance, 'sześciu' takes the locative form because it's used in a context following 'o', which requires the locative case.

• Zabrakło sześciu minut do końca.

  Six minutes were missing till the end.

  Here, 'sześciu' is used in the genitive form because it describes minutes in a context showing lack or deficit, which typically requires the use of the genitive case.