The Vietnamese word "thay" is a verb that generally means "to replace," "to substitute," or "to change." It can also mean "to moult" when referring to animals shedding their fur or feathers. Understanding this word can help you in various contexts in Vietnamese.
To Replace/Substitute: This is the most common usage of "thay." It means to take the place of something or someone.
To Change: It can also mean to change something, like changing clothes or changing one's mind.
To Moult: In the context of animals, it means to shed or lose fur, feathers, or skin.