Katakana, a set of Japanese syllabary characters, secondary to hiragana, derived from portions of Chinese characters whose sounds approximate the Japanese sound being represented. Chiefly thought of as being used for loanwords (cf. カタカナ語 (“loanword”, literally “katakana word”)), it has a number of other uses too, complementing hiragana; see Katakana#Usage on Wikipedia.Wikipedia

the Japanese language

kanji

a mixed script of kanji and katakana, or a use of such script, that was common in formal writing, before modern orthographic reforms which favored hiragana over katakana for grammatical elements such as particles and inflectional affixes

a letter or character (symbol for a sound or a word) / (linguistics) script, writing system / (specific to Japanese) a written mora, a kana / writing in general, written words

a letter, a character (symbol for a sound or a word) / (linguistics) script, writing system / (specific to Japanese) a written mora, a kana / writing in general, written words

Japanese-language education for non-native speakers

kanji approved for regular use by the 文部科学省 (Monbu-kagaku-shō, “Japanese Ministry of Education”)

Sino-Korean vocabulary or "Hanja-eo"

The iteration mark 々, which indicates that the previous kanji ought to be repeated.