A sketch (from Ancient Greek σχέδιος - schedios "temporary") is a fast freehand drawing that is not supposed to be a finished work. If in oil paint it is called an oil sketch. In general, a sketch is a quick way to practice an idea for later use. Artist's sketches usually serve as a way to try out different ideas and start a painting before starting a more finished work, especially when the finished work is costly and takes up time (as in the case of a large painting or fresco). Sketching eases an artist's ability to focus on the most important parts of a subject and is a main part of artistic learning for students.