Refers to a decisive moment or event that changes the course of a situation, career, or life.
That encounter became a turning point in my life.
The company grew rapidly after the success of its new product marked a turning point.
He reached a turning point in his life at age 40.
That encounter became a turning point in her life.
He seized the turning point brought on by losing his job.
Quitting his job brought a turning point to his career.
契機 is the more formal, often causal term for an occasion that triggers something, whereas 転機 specifically frames that occasion as a turning point in one's life or fortunes.
岐路 evokes a crossroads where one must choose a path, while 転機 is the moment the change itself actually occurs.
画期 is a literary noun for an era-defining turning point in history, whereas 転機 is the everyday word for a turning point in a person's life or a situation.
major turning point; significant turning point
Compound of 転 (turn, change) and 機 (opportunity, moment). The combination conveys a moment when circumstances turn or change significantly.