厄特沃什数（Eo）是流体力学中的无量纲，得名自匈牙利物理学家罗兰·厄特沃什（1848–1919）。此无量纲有另外一形式，称为邦德数（Bo），得名自英国物理学家Wilfrid Noel Bond（1897–1937）。

厄特沃什数和莫顿数可以用来描述在运动流体中泡泡或是水滴的形状。厄特沃什数可以视为是浮力和表面张力的比值。

以下是用邦德数表示的公式：

邦德数可以量测表面张力相较于彻体力的重要性，若邦德数高，表示物体不太会被表面张力影响，若邦德数低（一般至少要小于1）表示物体主要是受表面张力影响。中间值表示表面张力和彻体力达到某种平衡。

In fluid dynamics the Eötvös number (Eo), also called the Bond number (Bo), is a dimensionless number measuring the importance of surface tension forces compared to body forces and is used (together with Morton number) to characterize the shape of bubbles or drops moving in a surrounding fluid. The two names commemorate the Hungarian physicist Loránd Eötvös (1848–1919) and the English physicist Wilfrid Noel Bond (1897–1937), respectively. The term Eötvös number is more frequently used in Europe, while Bond number is commonly used in other parts of the world.