sleep

[BC_Programmer]

Yes. It is common to use the terms as if equal.
Bears hibernate.
Dogs sleep.

The two are not equivalent in any way. They have completely different definitions both when it comes to Animals as well as when it comes to computers (As defined in the ACPI specification!). People getting confused between them doesn't suddenly make the terms interchangable.

[Geek-9pm]

ACPI specification

https://en.wikipedia.org/wiki/Advanced_Configuration_and_Power_Interface

Intel, Microsoft and Toshiba originally developed the standard, while HP and Phoenix also participated later. In October 2013, the original developers of the ACPI standard agreed to transfer all assets to the UEFI Forum, in which all future development will take place.[3] The latest version of the standard is "Revision 6.1", which was published by the UEFI Forum in March 2016.[4]

G1, Sleeping: Divided into four states, S1 through S4:

    S1, Power on Suspend (POS): Processor caches are flushed, and the CPU(s) stops executing instructions. The power to the CPU(s) and RAM is maintained. Devices that do not indicate they must remain on may be powered off.
    S2: CPU powered off. Dirty cache is flushed to RAM.
    S3, commonly referred to as Standby, Sleep, or Suspend to RAM (STR): RAM remains powered.
    S4, Hibernation or Suspend to Disk: All content of the main memory is saved to non-volatile memory such as a hard drive, and the system is powered down.

The above shows Hibernation to be a subset of Sleep. It is the fourth state of Sleep.
Recent article from MS:
https://msdn.microsoft.com/en-us/windows/hardware/drivers/bringup/overview-of-windows-support-for-acpi-5-0
Last Updated: 7/30/2016

Note Windows supports a subset of functionality defined in the ACPI 5.0 specification. Windows does not have an explicit check against higher revisions of the firmware. Windows will support firmware that conforms to higher revisions of the ACPI specification if this firmware contains the necessary support, as described in this design guide.

I did not see a reference thee to hibernation.
But elsewhere there are links that say Win 10 has it maybe.
http://www.techrepublic.com/article/investigating-sleep-states-in-windows-10/

Sleep states
When Windows enters sleep mode, it may appear that the system simply goes into a low power state and remains that way. However, the process is a bit more complex. The system actually goes through several levels of Sleep. These levels, or more specifically, power states, are defined by the Advanced Configuration and Power Interface (ACPI) specification. All told, the ACPI spec lists six states, which are numbered S0 through S5. We're mainly concerned about the Sleep states, but to keep everything in context, let's look at them all.

So there are five levels of sleep?

[Lorraine walsh]

They are not equal at all, in my view.  Sleep is a low power state from which the computer can quickly be awoken.  Hibernation is a fully powered down state and startup from hibernation requires significantly more time than sleep; startup time may be similar to a normal startup (startup from normal shutdown).

That looks a logical explanation. So does that mean that the sleep mode consumes less energy to that of the hibernation mode?

[soybean]

That looks a logical explanation. So does that mean that the sleep mode consumes less energy to that of the hibernation mode?

No, it's the opposite.  As I said in my previous post, hibernation is a fully powered down state.  In other words, you can unplug the computer, after it's gone into hibernation, and not lose any of your last work session (that you saved when the computer went into hibernation) when you restore power.   In contrast, sleep (sometimes also called Standby) mode does require some power.  If you unplug a computer in sleep mode, you will lose whatever apps/programs/windows you had open when it went to sleep.  For example, if you had a web browser open with 10 tabs open and a word processing program/app open when the computer went to sleep and you pulled the plug on it, you'd lose your work session; it would not be restored upon restoring power and starting your computer again.  But, with hibernation, you would not lose your work session; it would be restored the next time your turn on your computer.   

Note: hibernation does momentarily require more power when it is saving a session, compared to going into to sleep mode.  Sleep mode occurs immediately when it is invoked.  Hibernation takes a minute or two or longer, depending on your hardware specs and system configuration, because it saves a complete image of your work session to the hard drive. 

[soybean]

So there are five levels of sleep?

But, computer users have control over sleep and hibernation.   That's two levels.  So, from a practical perspective, we have two levels, not five.