Shut off x Shut down e Turn off x Turn down: A diferença

Qual a Diferenças entre shut off x shut down e turn off x turn down?

Thanks in advance.
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Hi there,

Shut down e shut off podem ser parecidas mas com diferentes usos. ;)

shut down (or shut something down)
Cease (or cause something to cease) business or operation.
The plant’s operators decided to shut down the reactor.
After dowloading shut it down immediately.
Close down, fold, close.
Cessar, desligar (muito usado para desligar maquinas que são operadas como o computador).

shut something off
Stem the flow of: "shut off the gas when you leave for a vacation"
Close off, cease, discontinue, lay off, quit, stop, give up - put an end to a state or an activity:
"Quit teasing your little brother."

Shut off - isolate or separate:
"She was shut off from the friends."
Divide, separate - make a division or separation

Shut off - block off the passage throughshut off - block off the passage through:
"We shut off the valve"
Block off, close off, barricade, block, block up, blockade, block off, bar, stop - render unsuitable for passage
"block the way"; "barricade the streets"; "stop the busy road"
Desligar, descontinuar, separar, terminar uma atividade, bloquear, etc.

turn down:
Decline an invitation. refuse - recusar
Turn the volume down. abaixar
She just turned me down. (dar o fora, recusar)

turn off
Cut - kill - stop: desligar, no sentido mais siples da palavra, cortar a energia, parar o funcionamento
"Turn it off now." Said the father.
"As you leave the room please turn it off."

Just to clarify my post, there are many other meanings worth seeing, right. :roll:

LOOK:
Shut Down
To be shut down is similar to being burnt (see 'burn'). This occurs when the first party is keen to do something, but the second party does not want to do it with that person, so they 'shut them down'. More often than not this happens involving trying to pick up with people of the opposite sex.
Greg: "Hey sweety, will you go out with me"
Laura: "I'd really like to, but I don't think we can"
... Greg just got SHUT DOWN!

Source: Urban Dictionary

Existem muitos outros significados, procurei aqueles que achei relacionados. OK.

Cheers!
Gostaria de saber se há diferença entre "shut down the computer" e "switch off the computer". Sei que os dois phrasal verbs significam "desligar", mas surgiu a dúvida. E por falar em "desligar", eu posso dizer "turn off the computer"?