/ ˈdreɪnɪdʒ; NAmE / noun [ U ]
1.
the process by which water or liquid waste is drained from an area :
a drainage system / channel / ditch
The area has good natural drainage.
2.
a system of drains
/ ˈdreɪnɪdʒ; NAmE / noun [ U ]
1.
the process by which water or liquid waste is drained from an area :
a drainage system / channel / ditch
The area has good natural drainage.
2.
a system of drains
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005