niihin

In a sentence

• Laitoin kirjat niihin laatikoihin, jotka olivat tyhjiä.

  I put the books into those boxes that were empty.

  'Niihin' is used here as an illative plural form of 'se', referring to the empty boxes as the destination of the action.

• Hän luotti niihin ihmisiin, jotka auttoivat häntä.

  He trusted those people who helped him.

  'Niihin' is employed as an allative plural form of 'se', indicating trust in a specific group of people.

• Minä mielelläni liityn niihin keskusteluihin, jotka käsittelevät kirjallisuutta.

  I am happy to join those discussions that are about literature.

  'Niihin' is used as an illative plural form of 'se', pointing to the specific discussions of interest.

• Olen lukenut ne kirjat, mutta en muista niiden sisältöä.

  I have read those books, but I do not remember their content.

  niiden is used as a possessive form referring to the contents of the plural noun.

• Katselen niihin ikkunoihin ja näen kauniita näkymiä.

  I look into those windows and see beautiful views.

  niihin serves as a directional pronoun indicating movement into the windows.

• Puutarhassa oli kukkia, ja kiinnitin huomioni erityisesti niihin keltaisiin.

  In the garden, there were flowers, and I paid attention especially to those yellow ones.

  niihin is used to refer to a specific group within the plural (yellow flowers).