Hello
salutation or greeting
Can your psychologist say hello to you while you are out at the supermarket?
Therapists are bound by confidentiality in all areas of their work.  It would violate the standard set by the APA for a therapist to acknowledge any client outside of a therapeutic setting.
What kind of code are therapists bound by in all areas of their work? Would it be in conformity to #1 to acknowledge a client outside a therapeutic setting?