A line is a continuous mark made on a surface. Think of a line as a moving dot.
In the Louisa Villea, line is used primarily to define the contours of the objects. Contour is the outline or edge of a figure or shape. Most importantly, line defines the appearance of Louisa herself. This painting started with a pencil line drawing of Louisa's face. Beginning with the eyes, it was important that the proportions were anatomically accurate in order to render the portrait in a realistic style.
A fine line continued the contour of her body keeping proportions accurate.
Definite lines were used to present the birds and the infant-like characteristics of the cherub in a realistic manner such as was used by the artists of the Renaissance period (1500's to 1800's).
In the background, the buildings of Louisville used lines that were less defined. The contours around and within the buildings are not as clean and straight. This loose definition presented the background (and even the bench) in a style similar to the Impressionist painters (late 1800's).
The dream-like, swirly lines and shapes throughout the painting are indicative of the style used by Abstract Expressionist painters (mid 1900's-).