|—n , pl -brae, -bras|
|1.||a region of complete shadow resulting from the total obstruction of light by an opaque object, esp the shadow cast by the moon onto the earth during a solar eclipse|
|2.||the darker inner region of a sunspot|
|[C16: from Latin: shade, shadow]|
|umbra (ŭm'brə) Pronunciation Key
Plural umbras or umbrae (ŭm'brē)
that part of a shadow in which all light from a given source is excluded. The shadow from a point source of illumination is essentially all umbra, but that from a source of some size (as from the Sun) consists of a small umbra and a much larger partial shadow called the penumbra. Thus, in an eclipse of the Sun, the regions within the umbra experience a total eclipse and those within the penumbra, partial eclipse. The term is also used for the dark central portion of a sunspot.
Learn more about umbra with a free trial on Britannica.com.