Hi
"Η δουλειά είναι χαρά" means "Work is a pleasure"
We use this phrase in order to say that having a job, an occupation, makes us creative and productive, therefore happy.
"Η δουλειά είναι μια χαρά" means "Work is just fine", "everything is going fine with work"
The expression "μια χαρά" is widely used in Greek meaning "fine", "well"
Examples:
"Τι κάνεις;" = How are you?
"Μια χαρά, ευχαριστώ" = Fine, thank you.
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Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.