Practice JLPTHow to tell them apart
と共に emphasizes that A and B share a property or act together, often in a lasting or inherent sense, while と同時に stresses that two actions or states occur at the same moment. Swapping them can sound unnatural: 建設的であると共に革命的だ works because the two qualities coexist, but 建設的であると同時に革命的だ highlights simultaneity rather than shared nature.
- と共に Use と共に when two things share a property or act together in an ongoing, inherent way.
- と同時に Use と同時に when two actions or states happen at the same moment or simultaneously.
| Grammar point | Meaning | JLPT level |
|---|---|---|
| と共に to ni | Together with; as; along with | N3 |
| と同時に to ni | At the same time as | N3 |
と共に to ni
Together with; as; along with
As well as; with; along with; at the same time; when, as; while | A phrase which is used to express the idea that A and B share a common property or do the same thing together, that two things take place at the same time, or that someone or something possesses two properties.
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その提案は建設的であると共に革命的であった。
The proposal was revolutionary as well as constructive.
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スタインベックはへミングウィイと共にアメリカの代表的作家の一人だ。
Steinbeck, as well as Hemingway, is a writer representative of American writers.
と同時に to ni
At the same time as
At the same time (as); at the time; when; as; while; as well as ~ | A phrase which is used to express the idea that someone does something or something takes place at the same time as another action or event, or that someone or something is in two states simultaneously.
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この新しい装置は安全であると同時に効率がいい。
This new equipment is safe and, at the same time, efficient.
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外国語を勉強する時は、文法を理解すると同時に文型の口頭練習もしなければならない。
When you study a foreign language, while you learn grammar, you must also practice sentence patterns orally.
と共に and と同時に are both JLPT N3 grammar points that Japanese learners often mix up. This page compares them side by side — meanings, usage and example sentences — so you can tell them apart.