A deep breath expressing tiredness, relief, sadness, or frustration. Often used in phrases like ため息をつく (to heave a sigh).
He let out a big sigh.
The scenery was so beautiful it made me sigh.
I was so tired that a sigh escaped me without meaning to.
He heaved a deep sigh when he saw his test results.
She let slip a sigh as she looked over the documents.
He said, sighing, 'I can't do this anymore.'