[[File:ESO- Reflection Nebula around HD 87643-phot-28a-09-fullres.jpg|thumb|right|upright=1.2|Nebulosity around the B[e] star HD 87643]]
A B[e] star, frequently called a B[e]-type star, is a B-type star with distinctive forbidden neutral or low ionisation emission lines in its spectrum. The designation results from combining the spectral class B, the lowercase e denoting emission in the spectral classification system, and the surrounding square brackets signifying forbidden lines. These stars frequently also show strong hydrogen emission lines, but this feature is present in a variety of other stars and is not sufficient to classify a B[e] object. Other observational characteristics include optical linear polarization and often infrared radiation that is much stronger than in ordinary B-class stars, called infrared excess. As the B[e] nature is transient, B[e]-type stars might exhibit a normal B-type spectrum at times, and hitherto normal B-type stars may become B[e]-type stars.
Discovery
Many Be stars were discovered to have spectral peculiarities. One of these peculiarities was the presence of forbidden spectral lines of ionised iron and occasionally other elements.