keep = donjon?

i am not sure i understand the word 'keep' well
terminology sais it is the fortifyed part inside a castle but don't explain any more about it
can you please explain more clearly what it is?
also is donjon=keep or there is any small difference between them?
explain me please with more details!
thanx to everybody who will answer my question!

[Peter van der Wielen]

A keep and a donjon are the same. It is the big central tower of a castle, where the living quarters were established, and the last retreat during a siege.
The word donjon comes from dung, later dungeon. In the early days women were a wanted price, and needed special protection against invaders. They did this by digging a hole in the ground, closed with board and covered with dung. This 'dungeon' was the stay of the women. Later they build a tower over this dungeon, which the French called 'donjon'.
Lots of castles are developed from out of this tower. The cellars were mostly used as a real dungeon.

[Denis]

Yes, as far as I know, the words “keep” and “donjon” are synonyms.
A keep is the inner stronghold of a castle. Since it was the ultimate level of defence and often served as the landlord’s residence, it was usually the sturdiest and the most outstanding part of a castle.

You can see the photo of a crumbling keep here:

http://www.castlewales.com/keep.html

[Denis]

Wow! Your etymological reference to "donjon" is really interesting, Castle Ghost! I've never come across it before...
Cool!

thanx for answers!
but i have another question
can a castle have many keeps?

[Peter E Presford]

Not that I know of.
But the castle or fortification could have a very strong gateway complex that could double as a keep. Even wall-towers may reach the strength of a keep. In fact some early keeps may have started off as a wall or entrance tower
Peter

[Denis]

Well… a keep is a keep! Its singularity of stateliness and endurance actually make it distinct from all the other parts of a castle. Since a keep was in most cases designed as residence (though not as lavish as in a palace) and ultimate retreat for a feudal lord, and because the latter was ONE and grand, the keep was generally unique and imposing too! I suppose that is the simple truth of the notion…

Nonetheless, as Peter Presford has mentioned, many gate towers (usually double towers) sometimes merged into heavily fortified structures to eventually resemble / serve as keeps!

[Peter E Presford]

Think I brought Denbigh castle up on the site before.
But the triple tower gatehouse complex, with its banded stonework is stunning. And built instead of a normal keep.
A great pity it is in such a ruined state.
Peter

[Denis]

Yes, Peter! Denbigh is certainly a good point to mention here!
However, unfortunately, it is severely dilapidated now, and it is tough to discern the exact structure of the triple-towered gatehouse on a photo. Perhaps this would be simpler if seen in reality, but the photos can hardly convey a good image of its architecture. Do you happen to have a picture of what it looked like in pristine condition? … or, at least, in slightly better condition? It would be a very illustrative thing to display for this discussion!

thanks for all you help!
now i have another more question about keep
were is keep positioned in a castle and what does this position symbolize?