Translation guide
The English adverb "mainly" is used to indicate that something is true for the most part, or that something is the primary reason, component, or focus. In Japanese, this concept is expressed through various adverbs and grammatical patterns depending on the nuance.
Expressing that something is true in most cases or that something consists mostly of a particular element.
The most common and neutral way to say 'mainly' or 'primarily'. Used in both spoken and written Japanese.
この店は主に若い人に人気があります。
This shop is mainly popular with young people.
私は主に週末に買い物をします。
I mainly do my shopping on weekends.
Means 'mostly' or 'for the most part'. More casual than 主に and often used in conversation.
仕事は大体終わりました。
I've mainly finished my work.
Literally 'for the most part', emphasizing the large proportion. Slightly more formal.
その問題は大部分は解決しました。
The problem has been mainly resolved.
Indicating the primary cause or reason for something.
A clear pattern meaning 'the main reason is...'. Use this when you want to explicitly state the primary cause.
遅刻した主な理由は電車が遅れたからです。
The main reason I was late is that the train was delayed.
Formal adverb meaning 'mainly' or 'chiefly', often used in written contexts to indicate the primary factor.
この問題は主として経済的な要因によるものです。
This problem is mainly due to economic factors.
Describing the primary component or ingredient of something.
Pattern meaning 'centered around' or 'mainly consisting of'. Very natural in Japanese.
このクラスは留学生が中心です。
This class mainly consists of international students.
Means 'almost all' or 'mostly'. Used when the proportion is very high.
参加者はほとんど女性でした。
The participants were mainly women.
主に (omoni) is the most direct translation of 'mainly' and is neutral in register. 大体 (daitai) is more casual and implies 'roughly' or 'for the most part'. ほとんど (hotondo) means 'almost all' and is used when the proportion is very high, close to 100%.
English often uses 'mainly because' in casual speech. In Japanese, directly translating this as 主に〜から is unnatural. Instead, use patterns like 主な理由は〜からです or simply state the reason with から and rely on context.