Translation guide
The English word "main" has several distinct meanings. This guide covers the most common uses for learners: primary/chief, the largest or most important part, a pipe for water/gas, and the open sea. Each meaning has different natural Japanese expressions.
Describing something as the most important or central element.
A pre-noun adjectival meaning 'main' or 'principal'. Used before nouns to indicate the primary thing among several.
主な理由はお金です。
The main reason is money.
主な観光スポットを教えてください。
Please tell me the main sightseeing spots.
More formal than 主な. Often used for 'main' in the sense of 'major' or 'key', especially in written or technical contexts.
主要な産業は農業です。
The main industry is agriculture.
Loanword from English. Very common in casual speech, especially for events, dishes, or themes.
今日のメインイベントは花火です。
Today's main event is the fireworks.
メインディッシュはステーキです。
The main dish is steak.
Referring to the bulk or principal portion of something, often in contrast to a smaller part.
Means 'most part' or 'the greater part'. Used when talking about the main portion of a physical object, group, or abstract whole.
仕事の大部分は終わりました。
The main part of the work is finished.
Refers to the main body or unit of something, as opposed to attachments or accessories. Often used for machines, devices, or organizations.
Referring to a principal conduit in a utility system.
The standard term for a main pipe or main line in plumbing, gas, or electrical contexts.
ガスの本管が破裂した。
The gas main ruptured.
Often used for 'main line' in transportation or utilities, emphasizing a trunk line from which branches extend.
Referring to the sea far from land, often used in literary or historical contexts.
Literary term for the ocean or the main. Rare in everyday speech.
船は大海原へと進んだ。
The ship sailed into the main.
主な (おもな) is more common in everyday speech and writing. 主要な (しゅような) sounds more formal and is often used in reports, news, or academic contexts. Both mean 'main' or 'principal', but 主要な can imply 'major' or 'key' among several important items.
主な原因は不明です。
The main cause is unknown. (neutral)
主要な原因は特定できませんでした。
The main cause could not be identified. (formal)
メイン is a loanword and is very common in casual contexts, but it can sound out of place in formal writing or when referring to abstract concepts like 'main reason'. In those cases, use 主な or 主要な.
掃除機の本体が重い。
The main body of the vacuum cleaner is heavy.
水道の幹線工事が行われている。
Construction is being carried out on the water main.