Γεια σου Ιάκοβε
Both "καλώς ήρθατε" and "καλώς ορίσατε" mean "welcome".
The only difference between them is that "καλώς ορίσατε" is older form and a bit more formal than "καλώς ήρθατε".
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Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.