1. hiragana (ひらがな): This is a syllabic script used primarily for grammatical particles, verb and adjective endings, and words that don't have kanji. It's considered the "cursive" script and is generally used for words of Japanese origin.
2. katakana (カタカナ): This is another syllabic script used for foreign loanwords, onomatopoeia, and emphasis. It's considered the "blocky" script and often gives a more "modern" feel.
3. kanji (漢字): These are logographic characters adopted from Chinese. They represent words and concepts, and each kanji can have multiple readings depending on context. While there are thousands of kanji, only a few hundred are considered essential for everyday use.
4. romanji (ローマ字): This is the Latin alphabet used to write Japanese. It's primarily used for transliteration and for situations where kanji or kana are impractical, such as in computer systems or for tourists.
Therefore, while hiragana, katakana, and kanji are the three main writing scripts used in Japanese, romanji is an essential part of the writing system as well. It's important to note that all four scripts are intertwined in written Japanese and often appear together in a single sentence.