telefon

In a sentence

• Mam nowy telefon.

  I have a new phone.

  The word "telefon" in this sentence is used as a noun to describe a physical object, the phone.

• Dzwonię do ciebie z mojego telefonu.

  I am calling you from my phone.

  Here, "telefonu" is in the genitive case, indicating possession or origin—it's my phone from which I'm making the call.

• Zapomniałem o telefonie.

  I forgot about the phone.

  In this example, "o telefonie" is in the locative case, used after the preposition "o" to indicate being concerned with or about the phone.