Furigana
Furigana (振り仮名?) is a Japanese reading aid, consisting of smaller kana, or syllabic characters, printed next to a kanji (ideographic character) or other character to indicate its pronunciation. It is typically used to clarify rare, nonstandard or ambiguous readings, or in children's or learners' materials. It is most often written in hiragana, though katakana is used in certain special cases explained later in the article. In horizontal text, yokogaki, the furigana is placed above the line of text, while in vertical text, tategaki, it is placed to the right of the line of text, as illustrated below. It is one type of ruby text. Furigana is also known as yomigana (読み仮名?) or rubi (ルビ?) in Japanese.
Read more about Furigana.