Which of the following best describes sfumato?

Sfumato is best described as a technique of blending colors for soft transitions, which allows for subtle gradations of light and shadow. This method creates a hazy, atmospheric effect in paintings, where outlines are less defined and the transition between colors is smooth. The term "sfumato" is derived from the Italian word "sfumare," meaning "to evaporate" or "to fade away." This technique is often associated with Renaissance artists, particularly Leonardo da Vinci, who utilized it to enhance realism and depth in his works. By employing sfumato, artists can create a sense of volume and three-dimensionality in their subjects, seamlessly merging colors to evoke the complexities of light and skin tones.

The other options represent different art concepts that do not align with the definition of sfumato. For instance, applying thick layers of paint refers to impasto, while abstract drawing and geometric abstraction involve different techniques focused on non-representational art forms.