There are many different Kanji, the exact number is not known but it is around 50,000. However, not all 50,000 are taught in schools. The government of Japan has set up a 1,945 basic kanji list (Jōyō Kanji) that those learning the language need to know. They are the ones most commonly used in newspapers and magazines, along with street signs and store signs. Kanji takes many years to learn. By the end of his school years a pupil should know about 1,850 kanji. A university graduate would need to know about 3000. If someone does not know the kanji for a word, they can write it in kana and it will be understood, but it is usually not the proper way to write it, however kana can have many meanings for the same word, so unless the person writes in kanji, we will not know what they are saying. 