Katakana

Katakana (片仮名?) are used to write the following:

transliteration of foreign words and names, such as コンピュータ (konpyūta, “computer”) and ロンドン (Rondon, “London”). (Some foreign borrowings that have become naturalized may not be rendered in katakana.) See also Transcription into Japanese.

commonly used names of animals and plants, such as トカゲ (tokage, “lizard”) and バラ (bara, “rose”), and certain other technical and scientific terms, such as mineral names

occasionally, the names of miscellaneous other objects whose kanji are rare, such as ローソク (rōsoku, “candle”)

onomatopoeia, such as ワンワン (wan-wan, “woof-woof”), and other sound symbolism

emphasis, much like italicisation in European languages.

Katakana can also be used to impart the idea that words are spoken in a foreign or otherwise unusual accent; for example, the speech of a robot.