Learn Writing In Japanese

Modern Japanese uses four different scripts:

Kanji 漢字 are Chinese characters adapted to write Japanese, used to write:
-nouns;
-stems of adjectives and verbs;
-Japanese names.

Kanji is definitely the most difficult of the three writing systems to master. While each kana symbol represents only one syllable, kanji characters represent ideas rather than just sounds, and each one usually has at least a couple different readings. These are the On-reading, which is the reading based on the Chinese pronunciation, and the Kun-reading, which is the Japanese-based reading(a kanji character could have more than one On- and Kun-reading.) Depending on how the kanji is used in a word or sentence determines which reading is used. Also, while kana symbols have less than 4 or 5 strokes each(strokes are the number of lines used to write the symbol), kanji characters could have anywhere from 1 to over 20 strokes! And lastly, there's one hiragana and one katakana symbol for each Japanese syllable...but there are nearly 2,000 kanji characters in general use today!

Hiragana 平仮名 is a syllabary, used to write:
-inflectional endings for adjectives and verbs (okurigana 送りがな);
-grammatical particles (joshi 助詞);
-Japanese words with no kanji, or where the author didn't know the kanji, or where the kanji is likely to be unknown to the intended readership;
-indications of how to read kanji (furigana ふりがな);
-some common words which are perceived as easier to read in hiragana than kanji: for example, takusan (many) is more frequently written たくさん instead of 沢山.

Hiragana is used for any Japanese origin word that does not have a kanji reading, or if the person writing does not know the correct kanji for the word. But it is mostly used for any Japanese word that is not a noun, verb, or adjective, specifically for Japanese particles, pronouns, conjunctions, interrogatives, and honorifics. Hiragana is also used for the congugated endings of verbs, adverbs, and adjectives.

Katakana 片仮名 is another syllabary, used to write:
-emphasized words, like italics in English text;
-words and names from foreign languages (see below for more)
-onomatopoeia;
-words pronounced in a robot-like manner (originating from the use of katakana by early Japanese computers).

Katakana is mostly used to write words that are not of Japanese origin, such as English names and words, or Japanese words that are adapted from English or another language. Examples would be the names "Tom" and "Linda" written in katakana as "Tomu" and "Rinda," and the word "anime" written in katakana because it is adapted from the English word "animation." So basically any word in Japanese that sounds like English(example: terebi = television, takushii = taxi, shawaa = shower, reezaa = lasar) is most likely written in katakana. In addition to writing non-Japanese words, katakana is also used to write fantasy-based words or names, made-up words, and sound effects. It can also be used to put an emphasis on certain words or make the words stand out, similar to writing words in all capital letters in English.

Rōmaji ローマ字 are Roman characters, used to write:
-numbers in horizontal writing (note that some people lump Arabic-derived European numerals (アラビア数字, 洋数字) in with romaji);
-international units of measurement;
-acronyms and initialisms.

Since all Japanese are taught English in middle school and high school, most Japanese can read rōmaji. As a result, the amount of rōmaji in Japanese has increased considerably in recent decades. Japanese popular music lyrics in particular increasingly contain English words and phrases. Foreign loanword (gairaigo 外来語) usage has both proponents and opponents in and out of Japan.