This is the 14113th most frequent Turkish word.
motosikletin
"Of the motorcycle" or "the motorcycle's."
Here, 'motosikletin' is used in the genitive form, indicating possession (the motorcycle's key).
Motosikletin anahtarını kaybettim.
I lost the motorcycle's key.
In this sentence, 'motosikletin' serves as the subject of a subordinate clause, where its descriptive quality (fast) is emphasized.
Motosikletin hızlı olduğunu biliyordum.
I knew that the motorcycle was fast.
Here, 'motosikletin' is used in the possessive form, indicating whose motorcycle it is ('your motorcycle').