How many radicals are there?
The Kangxi Dictionary, compiled in Qing-dynasty China, classifies radicals into 214 categories, and most modern Japanese and Chinese-character dictionaries still base their classification on this system.
Tips for guessing a kanji's meaning from its radical
Even for an unfamiliar kanji, knowing the radical can give you a rough sense of its meaning category. For example, characters with "氵" tend to relate to water or liquids, and those with "木" tend to relate to trees or wood.
Frequently Asked Questions
Can I still look up a kanji in a dictionary if I don't know its radical?
Most kanji dictionaries also include an index by total stroke count or reading, so you can look it up even without knowing the radical.
Can the same kanji be classified under a different radical in different dictionaries?
Yes — while the general concept of radicals is shared, dictionaries sometimes differ on which component of a particular kanji should be treated as its radical.