A radical is a root – that is, the source or origin of a plant. Biologists and farmers study the roots of plants to understand better how they grow and evolve over time.
Linguists have borrowed the concept of radicals from biologists to understand words better. For example, in English, the very word linguist can be better understood when you know that the root word lingua means "tongue" in Latin.
In Chinese, too, understanding the roots of words helps make sense of them. Historically, Chinese scholars have recognized precisely 214 radicals that form the basis of a wide variety hànzi. Many of these radicals stand alone as characters, while others are found only within other characters. Additionally, some radicals also appear in recognizable alternative forms when placed within a character.
For example, consider the character 手, which is both a word unto itself ("hand," pronounced shou in Mandarin) and a character that is used to build other multiple character words, such as 手机 ("cell phone," pronounced shǒujī in Mandarin). Additionally, in its alternative form, this radical appears on the left side of a variety of characters, such as 打 ("to hit," pronounced da in Mandarin), which you learned in Chapter 3.
Similarly, the character 人 ("person," pronounced ren in Mandarin) is both a one-character word and a character that appears in other words, such as 大人 ("adult," pronounced dàren in Mandarin). You can also find it as a right-side radical within 认 ("recognize," pronounced ren in Mandarin). However, when appearing as a left-side radical, a more compact form is used. Thus, character 什 ("what," pronounced shén in Mandarin), which you learned in Chapter 2, includes this radical.
Look again and you'll also see that right side of the character 什 also incorporates 十 ("ten," pronounced shí in Mandarin).
Most complex Chinese characters of are really compositions of simpler characters, some of which you've already learned. In Part 3 of this book, you'll take a more ordered approach to radicals, using your knowledge of them to remember how to draw more complex Chinese characters.
For now, get ready to learn the remaining hànzi strokes, which make up the vast majority of Chinese characters, in Part 2.