上 [6] [v] fit; install; apply; put on
門 - door(indirect object)
(被)上了 - (is) applied(v)
鎖 - lock (direct object)
"門(被)上了鎖" = "door is applied with lock"
It means either a lock is put on the door or the door lock is set to locked state
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門 - door(object)
(被)鎖上了 - (is) locked(v)
"門(被)鎖上了" = "door is locked"
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門 - door(object)
是 - is (v)
锁著的 - locked (adj)
"門是锁著的" = "door is locked"
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锁著的 - locked (adj)
門 - door(n)
"锁著的門" = "locked door"