On one's own initiative (idiom)

●Without being prompted by others.

　　（主動地，自發地）

Examples:　　

1.In the absence of my commanding officer, I acted on my own initiative.　　

2.People will act on their own initiative and take what they believe to be appropriate actions.

On a whim (idiom)

●Based on a sudden, impulsive urge, desire, or idea.（一時的興致，突然的念頭）

Examples:　　

1.Major governmental policies cannot be decided on a whim; they have to be carefully and rationally thought through.　　

2.We booked the trip on a whim.

Punk (noun)

●A worthless person; a young thug.

（廢物，阿飛，混蛋）

Examples:　　

1.I think he was just trying to make me feel like a useless punk, since the only thing I've ever done with my own hands over any Thanksgiving was stuff a turkey.　　

2.The building was set on fire by a bunch of punks.

Be vested in sb/sth (phrasal verb)

●If power or authority is vested in someone or something, it is officially given to him, her, or it.

（賦予，屬於）

Examples:　　

1.In the United States, executive power is vested in the President. The control of this institution is vested in a board of trustees.

Lose one's head (idiom)

●To become confused, angry or emotional to the point where you cannot think clearly; to lose control and act irrationally.

（失去自制力，昏了頭）

Examples:　　

1.He usually stays quite calm in meetings but this time he just lost his head.　　

2.During their quarrel, he lost his head and started to beat her.