Παρακαλώ. (parakaló)
Please. / You're welcome. (one word in Greek; meaning depends on context)

Ευχαριστώ. (efcharistó)
Thank you.

Ευχαριστώ πολύ. (efcharistó polý)
Thank you very much.

Σ’ ευχαριστώ. (s' efcharistó)
Thanks. (informal)

Συγγνώμη. (syngnómi)
Sorry. / Excuse me.

Με συγχωρείτε. (me synchoreíte)
Excuse me. (more formal)

Συγγνώμη για την ενόχληση. (syngnómi gia tin enóchlisi)
Sorry for bothering you. / Sorry for the inconvenience.

Παρακαλώ πολύ. (parakaló polý)
You're very welcome. / My pleasure.

Δεν πειράζει. (den peirázei)
It's okay. / No worries. (literally: It doesn't matter)

Κανένα πρόβλημα. (kanéna próvlima)
No problem.

Φυσικά. (fysiká)
Of course.

Να ’στε καλά. (na 'ste kalá)
Be well. / Take care. (formal or plural)

Να είσαι καλά. (na eísai kalá)
Be well. / Take care. (informal; to one person)