noun
[ U , sing. ] a thing that tells you in advance that sth serious or dangerous is going to happen :
an early warning of heart disease
an early warning system (= of enemy attack)
noun
[ U , sing. ] a thing that tells you in advance that sth serious or dangerous is going to happen :
an early warning of heart disease
an early warning system (= of enemy attack)
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005