#extant garment

Walking dress, House of Worth, c.1895

Satin, velvet, silk taffeta.

Dinner dress is a type of evening dress, but since it was used for dinners, which was on the more intimate side of evening occasions, it was less formal. And being less formal it usually had long sleeves (during Late Victorian period you sometimes see examples of sleeves that are not full length, like elbow length) and more covering neckline than other evening dresses, though usually fully covering like day dresses. Here's some examples!

Extant garment from 1880-1885 (according to MET, to me it looks like 1887-89). Fashion plate from 1883 - in this one the dress on the left is a ball gown, the one on the right is a dinner dress. It's pretty common to have a ball gown and a dinner dress in the same plate.

Fashion plate from 1892. Fashion plate from 1896 - again the dress in the left looks like a ball gown, while the dress on the right is a dinner dress.

Dinner dress can be sometimes hard to distinguish from some more formal day dresses, but if there's some visual context (like it's a fashion plate or painting), no hat and a fan are pretty good signs of it being an evening dress. Otherwise you might need some textual context. For example these three fashion plates (in the first one I'm talking about the dress on the left, in the last one also the one on the left), all from 1895 have same length of sleeves and same coverage of neck. However in the first plate the woman is holding an umbrella and a hat (even if it's not in her head), in the second plate the woman is holding a fan and not wearing a hat and in the third one she's not wearing glows and she is clearly receiving a guest in a visiting gown. Also the hem is a bit shorter in the first one which does imply walking skirt, and the style is a little plain for dinner, and in the last one the bodice is not made to look like part of the same dress as the skirt (it's giving very fancy version of skirt and shirtwaist combo).

In the mid 1890s it's also sometimes hard to distinguish dinner dresses from the ball gowns, since the poof of the sleeve got so large, they became actually pretty long too, and the fashionable necklines did rise a bit as well. For example compare the first plate from 1893 here to the second. Is it a Dinner dress? I think so, it has a little too high neckline for a ball gown, but when compared to the second plate from 1894 which I'm pretty sure is a ball gown, it's really not that far.

1901 silk reception gown

Gown of Countess Palatine Dorothea Sabina of Neuburg

olive green silk velvet with gold trim, sleeves with yellow, slashed atlas silk lining, green taffeta underskirt decorated with silver lace

c. 1598

From the burial place of the Counts Palatine of Neuburg in Lauingen, Germany

evening dresses belonging to V. V. Karakhan (Vera Viktorovna Karakhan)

Dress, 1836-40

Textured cotton printed with red and purple florals.

Negligée, c.1900

Silk and cotton

Kingsbury velvet gown, c.1870

Velvet, silk, floral lace, satin ribbon, petersham ribbon, tarlatan, baleen bones.