Actual Size ~ The measured size of an object.

Aerial Perspective ~ Creating a sense of depth in painting by imitating the way the atmosphere makes distant objects appear less distinct and more bluish than they would be if nearby. Also known as atmospheric perspective.

Apparent Size ~ The size that something appears to be. A tree in the distance may have an apparent height equal to the length of your thumb at arms length.

Apprentice ~ A person who agrees to work for someone else for a period of time in return for training in a trade or art. Leonardo was an apprentice to the artist Andrea del Verrocchio who taught him many things including how to paint, sculpt, and design buildings.

Archimedes Screw ~ An ancient device for lifting water. It consists of a spiral tube wrapped around an inclined rod. As long as the rod is turned, water enters through the open bottom end of the spiral and is slowly raised to the top where it pours out.

Automate ~ To invent a way in which some task usually requiring human labor can be done more efficiently by a machine. Leonardo invented several kinds of machines to automate the manufacture of objects such as needles and metal files.

Battlements ~ Protective stone railings built along the tops of castle walls with indentations through which soldiers can shoot while defending the castle.

Cartoon ~ A full sized design for a painting, ready to be transferred to a wall or canvas.

Cast ~ To make an object by pouring molten metal into a specially shaped mold and letting it harden.

Chiaroscuro (kee-ahr-uh-skew-roh) ~ A technique of painting in which the figures portrayed have no clear outlines. Instead they are shown emerging into the light from shadows. In Italian the word means "light-dark." Leonardo proved his expertise with this technique in The Mona Lisa and The Virgin of the Rocks.

Horizon Line ~ In perspective this line is drawn across the canvas at the viewer's eye level. It represents the line in nature where the sky appears to meet the ground.

Linear Perspective ~ A mathematical system for creating the illusion of space and distance on a flat surface such as a canvas or wall.

Middle Ages ~ The period of European history between the last Roman emperor and the Renaissance (476 A.D. to 1453 A.D.). The Roman Catholic Church was the most powerful authority during this period and new ideas and scientific observations which challenged the views of the Church were not encouraged or accepted.

Notary ~ A public officer who checks the authenticity of various legal documents such as business contracts and deeds for land before giving them an official seal.

Orthogonal Lines ~ Straight diagonal lines drawn to connect points around the edges of a picture to the vanishing point. They represent parallel lines receding into the distance and help draw the viewer's eye into the depth of the picture.

Patron ~ A person who supports an artist's work by providing the artist with money and/or food and shelter. When Duke Sforza's family fled Milan in 1499, Leonardo left to search for a new patron.

Peninsula ~ A long point of land extending into a body of water. The peninsula of Italy extends from Southern Europe into the Mediterranean sea.

Realism ~ The style of art in which the artist strives to make the painted scene look as real and natural as possible. Renaissance artists such as Leonardo became highly skilled at creating realism in their paintings.

Renaissance ~ The period of Western European history stretching from the early 14th century to the mid to late 16th century (early 1300s to mid to late 1500s). "Renaissance" comes from a French word meaning "rebirth." The term describes the movement that led to new interest and achievement in art, literature, and science. During this time scholars again began studying and discussing the original writings of the ancient Greek and Roman philosophers. New translations of ancient books became available. In Italy, and later in Northern Europe, painters and sculptors began studying nature more closely and using what they observed in their art. They also looked back to the art of ancient Rome for inspiration. Architects and engineers applied new techniques together with their own artistic style to create marvelous structures unlike any seen before.

Roman Catholic Church ~ A form of the Christian church headed by the Pope. The Roman Catholic Church was the only Christian religion in Western Europe during the Middle Ages and the Renaissance and held a great deal of power.

Sfumato (sfoo-mah-toe) ~ Italian for "smoky." A oil painting technique in which the artist coats the objects in a picture with layers of very thin paint to soften edges and blur shadows. This creates a dreamlike effect of atmospheric mist or haze. Leonardo was the most skilled practitioner of sfumato in the Renaissance. This technique can be seen in his paintings The Virgin of the Rocks and The Mona Lisa.

Symbolism ~ A form of art in which symbols are used to represent ideas. Painters in the Middle Ages relied on religious symbols to tell the stories in their paintings.

Three Dimensional ~ Having height, width, and depth. A box is three dimensional.

Two Dimensional ~ Having height and width only. A painting of a box is two dimensional.

Vanishing Point ~ The single point in a picture where all parallel lines that run from the viewer to the horizon line appear to come together. The vanishing point is generally placed at the viewer's eye level.