The Greek noun mnemeion means a tomb, a grave, or a memorial monument. It comes from the root mneme (memory), since tombs were monuments to remember the dead. In the Gospels, mnemeion is the word used for the tomb of Jesus — making it the most theologically significant mnemeion in history.
The empty mnemeion is the pivot of the entire gospel. Jesus raised Lazarus from his mnemeion (John 11). He himself was buried in a new mnemeion and rose from it on the third day. The tomb that was meant to be the final memorial became instead the proof of resurrection. The resurrection of Jesus does not abolish the mnemeion — it transforms its meaning from 'he is here' to 'he is not here, he has risen' (Matthew 28:6).