noun
one mind; wholeheartedness; single-hearted devotion
Refers to a state of being of one mind, wholeheartedly devoted to something, or acting with complete sincerity and unity of purpose. Often used in contexts of dedication, prayer, or collective resolve.
彼は一つ心で研究に打ち込んだ。
He devoted himself wholeheartedly to his research.
皆が一つ心になって被災地を支援した。
Everyone came together as one to support the disaster area.
Similar meaning of wholeheartedness, but 一心 is more common and can also mean 'one heart' in a more abstract or religious sense. 一つ心 emphasizes a unified, collective mindset.
A common phrase meaning 'to unite one's hearts' or 'to be of one mind'. 一つ心 is a noun form that encapsulates this idea.
Compound of 一つ (ひとつ, 'one') and 心 (こころ, 'heart, mind'). The exact historical derivation is uncertain, but the word literally means 'one heart/mind' and has been used to express unity of purpose or wholeheartedness.