脱だっ線せん

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Common wordJLPTN2Freq.FrequencyTop 20,000

脱線する · noun or participle which takes 'suru'

Meanings

derailment; going off the rails

Literal use for trains, trams, etc. coming off the track. Also used figuratively for plans or situations going awry.

digression; going off topic

Used when a conversation, discussion, or thought strays from the main subject.

〈物もの〉が脱だっ線せんするfor a train (or similar) to derail
強きょう風ふうで電でん車しゃが脱だっ線せんした。
The train derailed due to strong winds.
話はなしが脱だっ線せんするfor a conversation or talk to go off topic
先せん生せいの話はなしがいつも脱だっ線せんして授じゅ業ぎょうが終おわらない。
The teacher's talk always goes off on tangents, so the class never ends on time.
脱だっ線せんして〈事こと〉を話はなすto digress and talk about something else
会かい議ぎが脱だっ線せんして昔むかしの思おもい出で話ばなしになった。
The meeting drifted off topic and turned into old memories.

逸いつ脱だつ sense 2
逸脱 refers to deviating from a norm, rule, or standard in a formal or abstract sense, while 脱線 is more concrete (a train derailing) or casual (a conversation drifting off topic).
余よ談だんN1sense 2
余談 is the noun for the tangential remark itself, whereas 脱線 describes the act or process of straying from the main topic.
迷めい走そう sense 1
迷走 emphasizes aimless wandering or erratic movement (e.g. a typhoon or a stalled plan), while 脱線 emphasizes a sudden departure from an intended track or subject.
横よこ道みちN1
脱線 describes a conversation or train of thought derailing, a more dynamic image than 横道's simple 'straying onto a side path'.
逸それるN2
脱線する is used specifically for a conversation or train of thought derailing, a narrower and more idiomatic word than the general 逸れる.

脱だっ走そうN1
脱走 means to escape or flee (e.g. a prisoner), while 脱線 means to derail or digress; they share the kanji 脱 but describe unrelated actions.
脱だつ落らくN1
脱線 means derailing (a train) or going off topic, while 脱落 means dropping out, being omitted, or falling off—easy to confuse because both start with 脱.

Compound of 脱 (escape, remove) and 線 (line, track). Literally 'leaving the line/track'.