noun
slightest connection; sliver (of hope)
Used in literary or formal contexts to describe a very faint, slender, or barely perceptible thread of something, often hope, connection, or life. Common in set phrases like 一縷の望み (a ray of hope) or 一縷の望みもない (not even a glimmer of hope).
彼は一縷の望みを捨てなかった。
He did not give up even a sliver of hope.
生存者との一縷のつながりも途絶えた。
Even the slightest connection with the survivors was lost.
noun
one thread
Original literal meaning: a single thread. Now rare and mostly encountered in classical or explanatory contexts. In modern Japanese, the figurative sense (sense 1) is dominant.
「一縷」は文字通りには一本の糸を指すが、現代では比喩的に使われることが多い。
Literally, 一縷 means a single thread, but in modern usage it is mostly used figuratively.
一抹 (a touch, a tinge) is used for a faint amount of an emotion or quality (e.g., 一抹の不安), while 一縷 emphasizes a slender, thread-like connection or hope.
一筋 (a single line, a streak) can be used for a ray of light or a single-minded pursuit, but 一縷 is more literary and focuses on the fragility or thinness of the thread.
From the kanji 一 (one) and 縷 (thread). The figurative sense of a slender connection or faint hope developed from the literal image of a single, fragile thread.