Insidious

adjective
/ɪnˈsɪd.i.əs/
Proceeding in a gradual, subtle way but with harmful effects; operating or developing so stealthily as to be well established before becoming apparent or dangerous. Also used of a person or scheme that is treacherous or working by entrapment.

✍️ Usage in a UPSC answer

The most insidious threat to constitutional democracy is rarely an overt coup but the slow, lawful erosion of institutional checks, which hollows out accountability long before citizens recognise that their liberties have been compromised.

Synonyms

stealthysurreptitioustreacheroussubtlecreepingbeguiling

Antonyms

overtforthrightconspicuouscandid

🌱 Word Family

insidiously (adv), insidiousness (n)

🔡 Root

Latin insidiosus = cunning, treacherous; insidiae = ambush; in- = in; sedere = to sit

📜 Etymology

From Latin insidiosus 'cunning, treacherous', from insidiae 'ambush, snare, plot', from insidere 'to sit in/lie in wait for' (in- 'in, on' + sedere 'to sit'); entered English in the 1540s, partly via French insidieux.

🧠 Memory Hook

Think 'inside-ious': the danger sits INSIDE (Latin insidere, 'to sit in / lie in wait'), like an ambush hidden within — harm working quietly from inside before you notice.

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