grammar - What is the significance of の in 「鳥の詩」?

I've seen it used in many places, and sometimes it feels like a connection between words.

For example in 「鳥の詩」 (tori no uta), it looks as if the の is connecting 鳥 (tori) and 詩 (uta), and I would like to know what it represents, in this case at least.

Answer

The particle の "no" is mainly used to indicate possession, it's also called the possession indicator. An example could be:

先生／私／和子の車。[sensei/watashi/Kazuko no kuruma.] (Teacher's/my/Kazuko's car.)

Or linking nouns like:

車のトヨタ [kuruma no Toyota] (Toyota the car [company])

For other usages as well, see here.

I'll directly paste them from this site here:

1. 
   

   It can sometimes replace ga, and is used especially in clauses that modify a noun:
   
   Hontou ni mondai no nai tabi deshita. (It really was a trouble-free trip.)
   Watashi no oshieru gakusei wa, eigo no dekinai ko bakari desu. (None of the kids that I teach can speak English.)

   
   


2. 
   

   It comes after some adjectives: Kyoto no matsuri ni takusan no hito ga ita. (Many people were at the festival in Kyoto.) Kumi wa midori no fuusen ga hoshii. (Kumi wants a green balloon.)

   
   


3. 
   

   It makes informal questions: Yuushoku wa tabenai no? (Aren't you going to eat dinner?)
   Nanji ni kuru no? (What time will you come?)

   
   



4. 
   

   And it is also used between prepositions and nouns to make the noun the object of the preposition.

   
   
   
   
   • Compare the following sentences: Kono tegami wa Yuuko kara kita. (This letter came from Yuuko.)
     Kore wa Yuuko kara no tegami desu. (This is a letter from Yuuko.)
   
   
   • And these:
     Kono tegami o Yuuko ni okuru. (I'm going to send this letter to Yuuko.)
     Kore wa Yuuko e no tegami desu. (This is a letter to Yuuko.)
   
   
   
   

Note: Ni is not used with no in this way.