A taxi sign apparatus for a vehicle - having, on the one hand, an elongated roof sign body for signaling a functional state of a taxi and - having, on the other hand, a roof sign carrier for supporting the roof sign body on a roof area of the taxi, - such that the roof sign body consists of a base portion for receiving at least one light source in a first longitudinal section of said roof sign body and of a roof sign portion in a second longitudinal section which adjoins the first longitudinal section in longitudinal extension, - such that the base portion of the roof sign body carries a light source carrier and/or the light source, such that the light beam which is radiated from the at least one light source is emitted in the direction of the roof sign portion, - such that the base portion of the roof sign body is integrally connected to the roof sign carrier, - such that the roof sign carrier is formed as a support pedestal, said support pedestal being attachable to the roof area in a force-locking and/or interlocking manner, in particular in a latching or clamping manner, or by means of a magnetic force, - such that the roof sign portion is formed as a light hood, said light hood being attached with the opening rim thereof to the base portion of the roof sigh body in longitudinal extension, - such that the roof sign portion is hollow and has, on at least one longitudinal side (11, 12), a roof sign which is able to be illuminated from behind for signaling the functional state of the taxi and forms an illuminated surface when the light source is switched on, wherein the roof sign portion has light-impermeable and/or opaque surfaces on the one hand and translucent surfaces on the other hand to form the roof sign. - having, on the one hand, an elongated roof sign body for signaling a functional state of a taxi and - having, on the other hand, a roof sign carrier for supporting the roof sign body on a roof area of the taxi, - such that the roof sign body consists of a base portion for receiving at least one light source in a first longitudinal section of said roof sign body and of a roof sign portion in a second longitudinal section which adjoins the first longitudinal section in longitudinal extension, - such that the base portion of the roof sign body carries a light source carrier and/or the light source, such that the light beam which is radiated from the at least one light source is emitted in the direction of the roof sign portion, - such that the base portion of the roof sign body is integrally connected to the roof sign carrier, - such that the roof sign carrier is formed as a support pedestal, said support pedestal being attachable to the roof area in a force-locking and/or interlocking manner, in particular in a latching or clamping manner, or by means of a magnetic force, - such that the roof sign portion is formed as a light hood, said light hood being attached with the opening rim thereof to the base portion of the roof sigh body in longitudinal extension, - such that the roof sign portion is hollow and has, on at least one longitudinal side (11, 12), a roof sign which is able to be illuminated from behind for signaling the functional state of the taxi and forms an illuminated surface when the light source is switched on, wherein the roof sign portion has light-impermeable and/or opaque surfaces on the one hand and translucent surfaces on the other hand to form the roof sign.