Διατεθειμένος is the one who is willing to do something.
From the ancient Greek διατίθεμαι : διά + τίθεμαι
διά is a prefix
τίθεμαι (ancient Greek), which is the passive voice of the verb τίθημι = put/place.
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Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.