What are the three types of straight lines used in haircutting?

The three types of straight lines used in haircutting are horizontal, vertical, and diagonal.

Horizontal lines run parallel to the floor and are typically used to create width and fullness in a haircut. They can also help to create our desired shape, as they visually expand the hair's appearance in those dimensions. Vertical lines, running straight up and down, create length and are essential for adding movement to a style. They can also provide a sense of elegance to a haircut. Diagonal lines, which are slanted, offer versatility and can blend longer and shorter lengths more seamlessly, creating layers and movement within the hairstyle.

The other options describe different concepts not directly related to the types of straight lines in haircutting, such as styles or lengths rather than the fundamental lines used to shape hair.