Words Written Without Kanji in Japanese

In Japanese, most words are written with kanji, but sometimes a word is written with kana instead of kanji, be it with hiragana or katakana. This can happen for a number of reasons.

First off, some words simply do not have kanji, and if there's no kanji for the word, it's only natural that it can't be written with kanji. This case, however, is rather rare, as most common words do have kanji in Japanese.

Second, we have extremely simple, extremely common words, such as mama まま, for example. Since they're so common and simple, writing them with kanji feels like an overkill that'd make every phrase much harder to hand write. So such words get written with hiragana instead.

Likewise, suffixes are often written without their kanji. For example, nai 無い, "nonexistent," has a kanji, but it's rarely used as a lone adjective. It's far more common as an auxiliary adjective, like in shinai しない, "to not do." So that gets written as shinai しない, without kanji, and nobody ever writes it as shinai し無い.

Following this idea of not writing the complicate kanji when you don't need to, a number of words have kanji which are not part of the jouyou kanji, which'd be the kanji taught in school, or simply put have extremely unusual kanji people would have trouble recalling how to read. In such cases, the word may get written without kanji too.

This happens, for example, in words for names of animals, because the kanji of such words only ever show up in the names of the animals, and unless you're a veterinarian you'll rarely get to see them. So nezumi 鼠, "rat," may be written with katakana instead, as nezumi ネズミ.

The same thing may also happen to other simple words. For example, dame 駄目 and dame ダメ, or baka 馬鹿 and baka バカ. The kana version is just far simpler to write.

An extreme is the word for "rose," which is bara バラ, unless you want to waste your time trying to write it as bara 薔薇.

Finally, kanji may be avoided for aesthetic reasons. This is because kanji looks serious, katakana looks cool, and hiragana looks chummy, and sometimes you'd rather have your text looking cool or chummy than serious.