Other forms: sighs, sighing, sighed
A sigh is the long breath that comes out of you on its own — tired, relieved, or thoroughly fed up. You sigh at the top of the stairs with the shopping, sigh when the train is cancelled again, sigh into your coffee at the thought of Monday.
It is both verb and noun: he sighed, and then he let out a sigh. The feeling behind it lives in the sentence around it, so English marks it — a sigh of relief, a sigh of exasperation, a heavy sigh, a contented sigh. You can sigh AT something, or sigh over something you have no power to fix. Wind and trees sigh as well, in writing: the wind sighed in the pines means a soft continuous sound and no emotion at all. And to breathe a sigh of relief is the set phrase for the moment the danger passes.
1verbsighTo let out a long deep breath showing tiredness, relief or disappointment.
“She sighed and picked up the phone again.”
2nounaudibleA long audible breath of that kind.
“He answered with a sigh and reached for his coat.”
3verbwindOf wind or trees, to make a soft continuous sound.
“The wind sighed through the poplars all night.”
Sigh came from Middle English sighen, which grew out of sighte, the past tense of an older verb siken, from Old English sīcan. The oddity is that the past tense rebuilt the present: English reshaped the whole verb around the wrong form. Further back the trail thins out, ending in a possible Proto-Indo-European *seykʷ-, 'to pour out' — a breath poured out of you.
Proto-Indo-European
*seykʷ- — to pour out
Proto-West Germanic
*sīkan
Old English
sīcan
Middle English
sighen — to sigh
English, today
sigh
From Middle English sighen (“to sigh”), from sighte, past tense form of siken, from Old English sīcan, from Proto-West Germanic sīkan, perhaps ultimately from Proto-Indo-European seykʷ- (“to pour out”).
Etymology from Wiktionary, CC BY-SA