оних

In a sentence

• Sećam se onih dana kada smo igrali ispred kuće.

  I remember those days when we used to play in front of the house.

  The word "onih" is used here as a demonstrative adjective to refer specifically to certain days in the past.

• Pročitao sam sve knjige osim onih koje je preporučila profesorka.

  I have read all the books except for those recommended by the professor.

  Here, "onih" functions as a demonstrative pronoun to refer to specific books previously mentioned.

• Stari prijatelji govore o onih nekoliko godina provedenih zajedno.

  Old friends talk about those few years spent together.

  In this case, "onih" is part of a genitive phrase modifying the length of time referenced.