Difference between under, underneath and below?

[ROBINDESBOIS]

Who knows?

[bobjenkins]

Who knows?

Más o menos me parecen iguales

The shoes are under the bed
The shoes are underneath the bed
The shoes are below the bed
The shoes are beneath the bed



En unos casos uno puede sonar raro pero todas las palabras habrán entendido:)

[poli]

Who knows?
Bob tiene razón los significados son parecidos pero underneath, beneath, under es de bajo de (de bajo del alfombra Under the carpet, de bajo de la cama underneath the bed, beneath the surface de bajo de la superficie)
Below significa abajo (el piso abajo, the floor below)

[Rusty]

These three can be interchangeable in some instances. While the dictionary lists under and below as synonyms, I can think of cases when they are not. Underneath can be used as a noun. The other two can't. Below cannot be used as an adjective, but under and underneath can.

Let's have a look at some examples.

"That task is below me." (Meaning: I consider myself too good to do that type of work.) Here you can't use 'under' or 'underneath', but you could substitute the word 'beneath' with no problem. Only things can be under or underneath you, not doing something.
In the idiomatic expression "He is under the weather," or "below the weather," you can't substitute 'underneath'.

"I am under average" is not wrong, but it's much more common to say, "I am below average."

"There's a racket (loud noise) below," is correct. "There's a racket under," is not. But you can say "There's a racket underneath." Using 'below' implies anywhere lower than the speaker, while 'underneath' implies a particular object only. 'Under' can be used in this instance only when it functions as a preposition and there's a prepositional object:
"There's a racket under the bed." =
"There's a racket below the bed." =
"There's a racket underneath the bed." =
"There's a racket beneath the bed."

"The keys are underneath my hat," means that you'll find the keys only by lifting the hat. "The keys are under the hat" could mean that they are physically below (at a lower level than) the hat, but plainly visible and you don't have to remove the hat to retrieve them. But, it is also OK to say, "The keys are under the hat," or "The keys are beneath the hat," and mean that the hat must be lifted up to get at them.

I'm sure others can think of differences. But, as I said at the first, there are times when the three are completely interchangeable.