kanji 漢字

The kanji 漢字 is one of the three Japanese "alphabets". Unlike the kana かな, the hiragana ひらがな and the katakana カタカナ, the kanji isn't actually a syllabic alphabet, but a collection of logograms, representing words, and ideograms, representing ideas and meanings, that even allow you to guess the meaning of a word from its kanji.

Also unlike the kana, the way a kanji character is read may vary depending on the word. A single kanji character may have multiple readings, which can be classified into kun'yomi 訓読み and on'yomi 音読み readings.

Sometimes kanji are accompanied by furigana 振り仮名 which tells the correct reading. Certain words contain okurigana 送り仮名 to help disambiguate the proper reading.
The parts of a kanji character are called "radical" and "components". Sometimes they can hint its meaning or reading.

Although plenty words are written with kanji in Japanese, some words do not have kanji, while others have a kanji so complex to write or difficult to read that they are written without kanji instead.

This is the case of words written without Jouyou Kanji 常用漢字, the around 2000 kanji officially considered normal to use day-to-day and taught in public schools.

There are some words that repeat themselves and would be written by spelling the same kanji twice. In these cases the 々 symbol is used. It's an iteration mark used to repeat the previous kanji. For example: nakanaka 中々, "considerably."