What's the difference between sketch and line drawing?

Sketch: It is a kind of painting method that completely uses lines to represent objects in Chinese painting. There are single hook and multi-hook. Hook a line into a single hook at a time, with one color of ink, or with two shades of ink according to different objects. Re-hook is to use light ink, and then re-hook part or all according to the situation. The lines do not overlap once according to the original road, and its purpose is to increase the texture and the change of light and shade, making the image more vivid. The double hook line must be smooth and natural, otherwise it will be stiff. It is very difficult to express the shape, spirit, light, color, body and texture of an object with lines. Because the choice is simple, and the relationship between virtual reality and density is deliberately compared, line drawing has the characteristics of simplicity and clarity. Sketch: Sketch is a form of expression with lines and faces. Every object has three parts under illumination: light and dark. From the deepest to the brightest, it is the boundary between bright and dark, dark, reflective, gray and bright. Try to avoid bright parts and dark parts when drawing (that is, there are too many lines without gaps and reflections). Sketch is the inevitable foundation of other arts, especially watercolor, oil painting, printmaking and sculpture (relief), and it is also the necessary foundation of sketch for graphic design. Although sketch is considered as a two-dimensional art, it does not need color and three-dimensional space, but it also implies both. To put it simply, line drawing is a single line drawing, which is simple, concise and clear, and is a part of China traditional painting. Sketch can be a single line drawing or a two-dimensional drawing, which has a higher degree of freedom and requires higher skills than line drawing.