Translation guide
The English word "concurrent" describes events, actions, or states that happen at the same time. In Japanese, there is no single direct equivalent; the best translation depends on whether you are talking about simultaneous events, overlapping time periods, parallel processes, or technical contexts like computing.
Use when two or more events or actions occur at exactly the same moment.
The most common and versatile word for "simultaneous" or "at the same time." Can be used as a noun or adverb (with に).
二つのイベントが同時に開催された。
Two events were held concurrently.
同時通訳
simultaneous interpretation
Literally "simultaneous progress," used when multiple tasks or projects are carried out at the same time.
複数のプロジェクトを同時進行で進めている。
We are advancing multiple projects concurrently.
Means "all at once" or "simultaneously" for a group action. Often used for coordinated events like attacks, launches, or announcements.
全国一斉に花火が打ち上げられた。
Fireworks were launched concurrently across the country.
Use when two time periods, schedules, or durations overlap partially or fully.
A natural way to say that two periods overlap. The verb 重なる means "to overlap."
会議の期間が重なっているので、両方には出席できません。
The conference periods are concurrent, so I can't attend both.
Specifically for schedules or appointments that conflict or overlap.
すみません、その日は別の予定と日程が重なっています。
Sorry, I have a concurrent appointment on that day.
Use for processes, systems, or tasks that operate alongside each other, often in computing or engineering.
Means "parallel" or "concurrent" in the sense of multiple things proceeding side by side. Common in technical and business contexts.
サーバーは複数のリクエストを並行して処理する。
The server processes multiple requests concurrently.
Literally "simultaneous execution," used in computing for concurrent execution of threads or tasks.
このプログラムは同時実行に対応している。
This program supports concurrent execution.
Loanword from English, used in specialized IT contexts (e.g., concurrent programming). Not common in everyday speech.
コンカレント処理の設計は難しい。
Designing concurrent processing is difficult.
Use when opinions, findings, or results are in agreement or coincide.
Means "opinions agree" or "are concurrent." Natural for expressing consensus.
両者の意見が一致した。
Their opinions were concurrent.
Formal term for "coincidence" or "agreement," often used in legal or academic contexts.
証言が合致する。
The testimonies are concurrent.
While 同時 is the closest equivalent, it is not always natural. For overlapping schedules, use 重なる instead of 同時. For parallel processes, 並行 is often better.
同時 emphasizes exact simultaneity (same instant). 並行 emphasizes parallel progression over time. Use 同時 for events that happen at the same moment; use 並行 for tasks that run alongside each other.