At once; immediately; right away — an adverb indicating prompt action or response (commonly used in written/formal contexts).
異常が見つかれば直ちに連絡してください。
If you find anything abnormal, please contact us immediately.
事故が起きたので直ちに現場へ向かった。
An accident occurred, so I headed to the scene right away.
この決定は直ちに効力を発する。
This decision takes effect immediately.
Directly; immediately in the sense of a direct connection — indicates that something directly leads to or results in something else.
その情報は直ちに判断を誤らせる可能性がある。
That information could directly cause a wrong judgment.
薬の副作用が直ちに体調に影響を与えた。
The drug's side effects immediately affected his condition.