Some words are only written in hiragana or katakana, while some words have kanji to simplify the writing (although sometimes the kanji is harder to write than the hiragana characters). When learning Japanese, I'd recommend you learn hiragana first and then kanji. Kanji is used mainly to make your sentences shorter, but one kanji can have several readings for it. A Japanese sentence never ever has all kanji. It consists of both kanji and hiragana, so I'd start with hiragana first and work your way up. Example 下 has a few readings such as か (ka), げ (ge), した (shita), しも (shimo), もと (moto), さがる (下がる, sagaru), ください (下さい, kudasai), おりる (下りる, oriru), etc. note: all the other characters besides 下 are hiragana. In a sentence (Note: Relationals are は/wa, の/no, etc.) 今日は金曜日です。Kyou wa kinyoubi desu. Today is Friday. 僕の名前は中谷ブライソンです。Boku no namae wa Nakatani Bryson desu. My name is Bryson Nakatani (boku=male form of I) If you can read hiragana, you'd notice that although は is ha in hiragana, but in sentences it's pronounced as wa because it's a relational. This is one of the reasons why I believe learning hiragana is really important to learn first. It has its own rules, and you should learn it first because of this. If you start with kanji, you'll have to learn backwards, which can be pretty difficult. Dialogue 何時ですか。Nan ji desu ka. What time is it? 三時五分です。San ji go fun desu. 3:05. Time (minutes) - WIth hiragana, you can clearly tell the difference between 分 (pun/fun), so it's easier to know when you'd say pun/fun. Of course when you're finished with figuring out when to say it correctly, you should use the kanji, but hiragana is good for beginners in Japanese :) 1) いっぷn ippun 2) にふん nifun 3) さんぷん sanpun 4) よんぷん yonpun 5) ごふん gofun 6) ろっぷん roppun 7) ななふん nanafun 8) はっぷん happun 9) きゅうふん kyuufun 10) じゅうっぷん jyuuppun Kanji is useful when you know how to use it and know its readings (onyomi and kunyomi), but if you don't know hiragana, you may be in a fix.

There's only one way to know: experience! That means studying as much as you can, and then eventually you'll get a feel for which words are written in kanji, hiragana and katakana (and sometimes words can be written in more than one!). Good luck!

After you learned the whole Kana (hiragana and katakana) the rest of writing letters are Kanjis There is too many words which you have to write them in Kanji and you will know which words only by looking and practicing dictation I can say all of the Verbs's and adjectives's (most of them) first syllabary is written by Kanji, such as 食べる (verb. means to eat) or 高い (adjective. means tall) Katakana is used to write non japanese names of people and nouns. For example the word "pen" is a foreign word, so is written by katakana ペン Also when you want to emphasison on a specific hiragana word Generally hiragana is used for prepositions (like に, と, か,...) and that batch of words which are not written by Kanji and Katakana For begining I highly recommend you to download "Wakan" dictionary http://wakan.manga.cz/?page=download Also "Google translate" is another good source. (but only as a dictionary)

Hi. It's a very difficult question, because it depends on the writer, and written stuffs. Usually Japanese speakers write sentences on the rule below. hiragana: a postpositional particles, conjugational endings added after kanji, words which are not on the List of jōyō kanji. katakana:loan words except Chinese kanji : other (see; http://en.wikipedia.org/wiki/List_of_jōyō_kanji) Though you don't have to follow this rule. For example, although "明日(ashita/asu)", "事(koto)", "考える(kanga-eru)" are all on the list, you can write "ashita no koto o kangaeta (I thought about tomorrow)" like these below all 明日の事を考えた あしたの事を考えた あしたのことを考えた 明日の事をかんがえた