"Truly, He is Risen"
At the Coptic Church, Greek and Coptic responds are used:
Coptic:
ⲠⲓⲬⲣⲓⲥⲧⲟⲥ ⲁϥⲧⲱⲛϥ! Ϧⲉⲛ ⲟⲩⲙⲉⲑⲙⲏⲓ ⲁϥⲧⲱⲛϥ!
(Pikhristos Aftonf! Khen oumethmi aftonf!)
Greek (more common):
Christos Anesti ("Χριστός ἀνέστη!")
Wish you all the best for Easter. May God forgive us all.
Here is a little video about the meaning of Easter: