ノマ(Noma), Odoriji (踊り字, "dancing mark") , Kurikaeshi (繰り返し)

[별고을]

ノマ(Noma),  Odoriji (踊り字, "dancing mark") 

kasaneji (重ね字), kurikaeshikigō (繰り返し記号), or hanpukukigō (反復記号, "repetition symbols")

In Chinese, 𠄠 or U+16FE3 𖿣 OLD CHINESE ITERATION MARK (usually appearing as 〻, equivalent to the modern ideograph 二) or 々 is used in casual writing to represent a doubled character. However, it is not used in formal writing anymore, and it rarely appeared in printed matter. In a tabulated table or list, vertical repetition can be represented by a ditto mark (〃)

Iteration marks have been occasionally used for more than two thousand years in China. The example image shows an inscription in bronze script, a variety of formal writing dating to the Zhou dynasty, that ends with "子𠄠孫𠄠寶用", where the small 𠄠 ("two") is used as iteration marks in the phrase "子子孫孫寶用" ("descendants to use and to treasure")

々: 반복부호 (iteration mark)

島々  : しましま[島々]

日々  : ひび[日日]  매일 , 나날 

人々->人人 or 人びと' hitobito people

山々 yamayama mountains

次々 tsugitsugi one after another, in succession

少々- shoushou

tokidoki (時々, sometimes)

koko (個々, piece by piece; individually

kokkoku (刻々 こっこく,  moment by moment; hour by hour ) 

yokuyokujitsu (翌々日, lit. "next next day" (two days later))

共々 (ともども＝tomo-domo)

並々（なみなみ＝nami-nami)

呉々（くれぐれ＝kure-gure)

徐々に jojoni gradually, little by little

散々な sanzanna completely, terribly, etc.

* '僕らの日々'(보쿠라노히비/우리들의 나날)

The character "々" (々, often pronounced "noma (ノマ) " or "odori-ji (踊り字 ") is a Japanese kanji iteration mark. It signifies repetition or iteration, indicating that the preceding kanji or phrase should be repeated. 

 ノマ(noma)

々 is ‘kurikaeshi (繰り返し)' means the word before “々 “ repeats itself.

々, is also called, ‘noma(ノマ)' as it this kanji itself made up of 2 katagana letters “ノ + マ = ノマ (々)”.

Odori-ji  (踊り字; lit. dancing letter) :  one of the iteration marks which indicates to repeat the previous kanji, like a ditto mark (〃)

It's similar to the "ditto" mark (〃) in English. 

What is 「々」 and how does it affect meaning and pronunciation in Japanese?

The character 「々」, known as "repetition mark" or "dai" (打ち消し), is used in Japanese writing to indicate the repetition of the preceding kanji character. It is primarily employed to simplify the writing of words that contain the same kanji repeated.'

* うちけし[打(ち)消し, 打消] 부정 

 When same kanji is repeated, it emphasises the meaning of the first, or pluralize it.