靶恩（符号为b，也简称为靶）是一种面积单位，原先用于核物理中描述原子核及核反应的截面，今天则用于所有高能物理学领域中描述任何散射过程的截面，并通常能代表细小粒子发生相互作用的机率。一个靶恩的定义为10 m（100 fm），大约为一个铀原子核的截面面积。靶恩也在核四极共振和核磁共振中用作面积单位，量化核子与电场斜率之间的交互作用。虽然靶恩并不是国际单位制单位，但由于长期使用于粒子物理学而被承认。它是国际单位制所接受的少数单位之一，也是最近期被承认的（节和巴是其他可接受有限使用的非国际单位制单位）。

A barn (symbol b) is a unit of area. Originally used in nuclear physics for expressing the cross sectional area of nuclei and nuclear reactions, today it is also used in all fields of high-energy physics to express the cross sections of any scattering process, and is best understood as a measure of the probability of interaction between small particles. A barn is defined as 10 m (100 fm) and is approximately the cross-sectional area of a uranium nucleus. The barn is also the unit of area used in nuclear quadrupole resonance and nuclear magnetic resonance to quantify the interaction of a nucleus with an electric field gradient. While the barn is not an SI unit, the SI standards body accepts its use with SI units due to its continued use in particle physics.