NH2 meaning in Chemistry ?

The amino radical, •
NH
2, also known as the aminyl radical or azanyl radical, is the neutral form of the amide ion (NH−
2). Aminyl are highly reactive and consequently short lived like most radicals; however, they form an important part of nitrogen chemistry. In sufficiently high concentration, amino radicals dimerise to form hydrazine. While NH2 as a functional group is common in nature, forming a part of many compounds (e.g. the phenethylamines), the radical cannot be isolated in its free form.