Radicals or ‘bushu‘ form a noticeably meaningful part of a Kanji. Mostly dictionaries and books use around 214 to 250 radicals in order to group kanji. Radicals are very useful when it comes to memorizing kanji. They can be used to associate between a character and its meaning. For instance, the kanji for the word ‘chat’ 話 (hanashi) is made up of the radical 言 (gom ben) which means ‘to speak’ or ‘say’.
Radicals can be characters which do not appear by themselves or cannot be used independently, like 
(kusa kanmuri), 
(shin nyuu); or they could be independent kanji like 戸(to dare), 糸 (ito hen), 食 (shoku hen), 
(gyou gamae).
Radicals are usually classified into seven types depending on the position where they appear in a Kanji.
Hen are those radicals which appear on the left part of a Kanji. For example, 口 (kuchi hen, mouth) as in 味 (aji, taste), 糸 (ito hen, thread) as in 紙 (kami, paper), 金 (kane hen, money ) as in 鉄 (tetsu, iron), 禾 (nogi hen, grain along with the stalk) as in 私 (watashi, I).
Kanmuri or Gashira are those radicals which appear on the top part of a Kanji. For example, 
(ame kanmuri, rain) as in 雲 (kumo, cloud), 
(ana kanmuri, hole) as in 空 (sora, sky), 
(ami gashira, net ) as in 買う (kau, to buy), 
(take kanmuri, bamboo) as in 答え (kotae, to answer).
Tsukuri are those radicals which appear on the right part of a Kanji. For example, 
(chikara, power) as in 勤める (tsutomeru, to work), 
(san zukuri, hair decoration) as in 形 (katachi, shape), 
(ritto, sword ) as in 利 (ri, profit).
Ashi are those radicals which appear on the bottom part of a Kanji. For example, 
(yotsu ten ashi, fire) as in 蒸す (musu, to steam), 
(shitagi, tree) as in 葉 (ha, leaf).
Tare are those radicals which appear on the top and left part of a Kanji. For example, 戸 (to dare, door) as in 戻る (modoru, to return), 
(ma dare, store room) as in 座る (suwaru, to sit).
Nyou or Nyuu are those radicals which appear on the left and bottom part of a Kanji. For example, 
(shin nyou, proceed) as in 遊ぶ (asobu, to play), 走 (sou nyou, run) as in 起きる (okiru, to wake up).
Kamae are those radicals which either encircle the Kanji or appear on any other part not mentioned above. For example, 
(gyou gamae, go) as in 術 (jutsu, technique), 
(mon gamae, gate) as in 間 (aida, span/space), 口 (kuni gamae, country) as in 国 (kuni, country), 
(shiki gamae, ceremony) as in 式 (shiki, ceremony).
