Citadel:

a stronghold into which people could go for shelter during a battle

etymology: 1586, “fortress commanding a city,” from It. cittadella, dim. of cittade “city,” from L. civitatem (see city).

Castle: a large building formerly occupied by a ruler and fortified against attack; or a large and stately mansion.

castle

Etymology of the word castle:late O.E. castel, from O.N.Fr. castel, from L. castellum “fortified village,” dim. of castrum “fort;” cognate with O.Ir. cather, Welsh caer “town” (and perhaps related to castrare “cut off”). This word had come to O.E. as ceaster and formed the -caster and -chester in place names.

Castles are large defensive buildings, commonly stone but quite a few wooden ones have existed. If they had walls around the building itself it was only to defend the building itself. Citadel might incorporate a castle in them and are usually built with the purpose of defending a town or city, the word citadel is supposed to come from the latin civis, which means citizen. An example, Karak Castle was built ontop of a hill in a valley between Jerusalem and Egypt. Any people around there who wanted to hide behind walls would have to go into the castle itself. Jerusalem on the other hand had at least 1 castle in it and the people of the city didn’t have to go near it to be defended by the walls of their Citadel city.

Citadel is a fortress and a castle is a walled residence

A citadel is a miltary fort more or less. A castle could be a military fort, but it can also be just an opulent or a walled residence.

Like is defined in terms of more of a crush or affection/fondness. Love is the outworking of your truest feelings in your actions and behavior. If you really love someone, you strive to put their needs above your own. You might do that too if you like someone, but it’s not a long term thing. Good luck! Hope this helped.

they are like synonyms?