Line - is a mark on a surface that describes a shape or outline. It can create texture and can be thick and thin. Types of line can include actual, implied, vertical, horizontal, diagonal and contour lines. (note: Ken does not list "psychic line" - that was "new term" to me)
Color - refers to specific hues and has 3 properties, Chroma, Intensity and Value. The color wheel is a way of showing the chromatic scale in a circle using all the colors made with the primary triad. Complimentary pairs can produce dull and neutral color. Black and white can be added to produce tints (add white), shades (add black) and tones (add gray).
Texture - is about surface quality either tactile or visual. Texture can be real or implied by different uses of media. It is the degree of roughness or smoothness in objects.
Shape - is a 2-dimensional line with no form or thickness. Shapes are flat and can be grouped into two categories, geometric and organic.
Form - is a 3-dimensional object having volume and thickness. It is the illusion of a 3-D effect that can be implied with the use of light and shading techniques. Form can be viewed from many angles.
Value - is the degree of light and dark in a design. It is the contrast between black and white and all the tones in between. Value can be used with color as well as black and white. Contrast is the extreme changes between values.
Size - refers to variations in the proportions of objects, lines or shapes. There is a variation of sizes in objects either real or imagined. (some sources list Proportion/Scale as a Principle of Design)
These elements are used to create the Principles of Design. Principles are the results of using the Elements. When you are working in a particular format (size and shape of the work surface) the principles are used to create interest, harmony and unity to the elements that you are using. You can use the Principles of design to check your composition to see if it has good structure.