What are the differences/characteristics between katakana, kanji and hiragana?


I know that romaji is the conversion from those to the roman alphabet, but
what are the differences or characteristics between katakana, kanji, and
hiragana?

Are they used on a different context? Is one of them more formal than the
others? Do they have something in common?




I think the [Wikipedia article on the Japanese writing
system](http://en.wikipedia.org/wiki/Japanese_writing_system) explains it
pretty well, but to summarize:

  * Hiragana and katakana (collectively referred to as kana) are syllabic writing, that is, each character represents a syllable such as "ta" or "o". They're purely phonetic so they don't have direct connotations as kanji do, and both have the same set of syllables. In modern writing: 
    * Hiragana is generally used for Japanese words when they're not written in kanji, and for all the grammatical "glue" such as conjugations and particles.
    * Katakana is usually used for loanwords and onomatopoeia. There's no strict rule though, so you will see katakana used for other purposes as well, such as emphasis.
  * Kanji is ideographic writing, that is, each character represents a concept or an idea. For example, 水 means "water" while 朝 means "morning". Each character also has one or more readings, and the correct one depends on which word the kanji is part of. Many kanji (such as my two examples) can also act as stand-alone words.




I think the [Wikipedia article on the Japanese writing
system](http://en.wikipedia.org/wiki/Japanese_writing_system) explains it
pretty well, but to summarize:

  * Hiragana and katakana (collectively referred to as kana) are syllabic writing, that is, each character represents a syllable such as "ta" or "o". They're purely phonetic so they don't have direct connotations as kanji do, and both have the same set of syllables. In modern writing: 
    * Hiragana is generally used for Japanese words when they're not written in kanji, and for all the grammatical "glue" such as conjugations and particles.
    * Katakana is usually used for loanwords and onomatopoeia. There's no strict rule though, so you will see katakana used for other purposes as well, such as emphasis.
  * Kanji is ideographic writing, that is, each character represents a concept or an idea. For example, 水 means "water" while 朝 means "morning". Each character also has one or more readings, and the correct one depends on which word the kanji is part of. Many kanji (such as my two examples) can also act as stand-alone words.

