Each Chinese character is written as a fixed sequence of' strokes. There are very few basic types of strokes, each with its own prescribed direction, length, and contour. The dynamics of these strokes as written with a brush, the classical writing instrument, show up clearly even in printed characters. You can tell from the varying thickness of the stroke how the brush met the paper, how it swooped, and how it lifted; these effects are largely lost in characters written with a pen.
The sequence of strokes is of particular importance. Let's take the character for "mouth," pronounced kön. Here it is as normally written, with the order and directions of the strokes indicated.
If' the character is written rapidly, in "running-style writing," one stroke glides into the next, like this.

If the strokes were written in any but the proper order, quite different _ distortions would take place as each stroke reflected the last and anticipated the next, and the character would be illegible.
The earliest surviving Chinese characters, inscribed on the Shang Dynasty "oracle bones" of about 1500 B.C., already included characters that went beyond simple pictorial representation. There are some characters in use today which are pictorial, like the character for "mouth." There are also some which are directly symbolic, like our Roman numerals I, II, and III. (The characters for these numbers--the first numbers you learn in this course--are like the Roman numerals turned on their sides.) There are some which are indirectly symbolic, like our Arabic numerals 1,-2, and 3. But the most common type of character is complex, consisting of two parts: a "phonetic," which suggests the pronunciation, and a "radical," which broadly characterizes the meaning. Let's take the following character as an example. 
This character means "ocean" and is pronounced Xâng. The left side of the character, the three short strokes, is an abbreviation of a character which means "water" and is pronounced shui. This is the "radical." It has been borrowed only for its meaning, "water." The right side of the character above is a character which means "sheep" and is pronounced Xâng. This is the "phonetic." It has been borrowed only for its sound value, xâng. A speaker of Chinese encountering the above character for the first time could probably figure out that the only Chinese word that sounds like and means something like "water" is the 'word gâng meaning "ocean." We, as speakers of English, might not be able to figure it out. Moreover, phonetics and radicals seldom work as neatly as in this example. But we can still learn to make good use of these hints at sound and sense.
Many dictionaries classify characters in terms of the radicals. According to one of the two dictionary systems used, there are 176 radicals; in the other system, there are 21h. There are over a thousand phonetics.