Translation guide
The First World War (World War I) is typically referred to as 第一次世界大戦 in formal contexts, but in everyday conversation, 第一次大戦 or simply 大戦 may be used when the context is clear.
第一次世界大戦
First World War
The standard, formal name for the First World War in historical, academic, or official contexts.
The full, formal term for World War I. Used in textbooks, news, and official documents.
第一次世界大戦は1914年に始まった。
The First World War began in 1914.
A slightly abbreviated form, still formal but common in historical writing.
第一次大戦の影響は甚大だった。
The impact of the First World War was enormous.
Literally 'the Great War'. Can refer to WWI when context is clear, but may also refer to WWII or other large wars. Use with caution.
Ambiguous without context; usually refers to WWI in European history, but in Japan it might be unclear.
大戦中、多くの兵士が命を落とした。
During the Great War, many soldiers lost their lives.
When talking casually about the First World War, often the full term is still used, but abbreviations or contextual references are possible.
Even in casual speech, the full term is common and natural.
第一次世界大戦って、いつ終わったんだっけ？
When did the First World War end again?
WWI is 第一次世界大戦 (Daiichiji Sekai Taisen) and WWII is 第二次世界大戦 (Dainiji Sekai Taisen). The pattern is 第 + number + 次世界大戦. In casual contexts, they are often shortened to 第一次大戦 and 第二次大戦, or simply WWI/WWII when speaking with people familiar with English abbreviations.
第二次世界大戦は1945年に終わった。
World War II ended in 1945.
Japanese speakers often use the English abbreviation 'WWI' (ダブリュー・ダブリュー・ワン) in casual conversation, especially among younger people or in contexts where English loanwords are common. However, in formal writing or speech, the Japanese term is preferred.
Slightly shorter, acceptable in casual conversation among history buffs.
第一次大戦の映画を観たよ。
I watched a movie about the First World War.