1.
many; much; a large number; the majority
A large number or amount of something. Functions as a noun, often followed by の (多くの = many) or used with が/は as a subject meaning 'most' or 'the majority.'
多くの人が参加した。
Many people participated.
学生の多くは通学に電車を使っている。
Most of the students use the train to commute to school.
この地域では多くの場合、車がないと不便だ。
In this area, it's inconvenient without a car in most cases.
被害を受けた建物の多くは築30年以上のものだった。
Most of the damaged buildings were over 30 years old.
2.
mostly; for the most part; in many cases
Used adverbially to indicate that something is true in the majority of cases.
この地域では多くの場合、車がないと不便だ。
In this area, it's inconvenient without a car in most cases.
日本人は多く語らない。
Japanese people for the most part don't talk a lot.
休日は多くを家で過ごす。
I spend most of my days off at home.
The noun/adverb form of 多い (many). While 多い exists as an adjective, it cannot directly modify a noun — *多い人 is ungrammatical. Use 多くの instead.
KEY PATTERNS:
- 多くの + noun: many ~ (多くの人: many people)
- ~の多く: most of ~ (学生の多く: most students)
- 多くの場合: in many cases
- 多くを語らない: not to say much
COMMON MISTAKE:
Learners often write 多い人 instead of 多くの人 or 人が多い. This is one of the most common errors with 多い.