Similarly as in other languages, in Greek diminutives are root words with an extra suffix. We use them to convey the smallness of the object, tenderness, endearment but sometimes devaluation, too.
Diminutives of masculine words
For masculine we have the following endings: -ούλης, -άκης, -άκος
When we talk about our family members, we use the -ούλης, e.g., αδελφός – αδελφούλης (athelfós-athelfúlis), πατέρας – πατερούλης (patéras-paterúlis), παππούς – παππούλης (papús-papúlis).
Usually for names, we use -άκης, for example: Δημήτρης – Δημητράκης (thimítris-thimitrákis), Γιάννης – Γιαννάκης (ghiánis-ghianákis), Γιώργος – Γιωργάκης (ghiórghos-ghiorghákis).
Last, different other nouns can fall in the category -άκος, for example άνθρωπος – ανθρωπάκος (ánthropos-anthropákos), δρόμος – δρομάκος (thrómos-thromákos), κήπος – κηπάκος (kípos-kipákos).
Diminutive for feminine words
Endings: -ούλα, -ίτσα
Equally, for family members we use -ούλα, e.g., αδελφή – αδελφούλα (athelfí-athelfúla), μάνα – μανούλα (mána-manúla), κόρη – κορούλα (kóri-korúla), but also for names Μαίρη – Μαιρούλα (méri-merúla), Κατερίνα – Κατερινούλα (katerína-katerinúla).
As for -ίτσα, there is no specific rule. We can only say that these endings are interchangeable, but usually one version sounds better. For example, φούστα – φουστίτσα (fústa-fustítsa), κοπέλα – κοπελίτσα (kopéla-kopelítsa), but καρδιά – καρδούλα (karthiá-karthúla), not «Καρδίτσα» (karthítsa) because that’s a city in Greece, and νύφη – νυφούλα (nífi-nifúla), not «νυφίτσα» (nifítsa) because that’s a “weasel”!
Diminutive for neutral gender
Ending: -άκι
σπίτι – σπιτάκι (spíti-spitáki), κορίτσι – κοριτσάκι (korítsi-koritsáki), γατί – γατάκι (ghatí-ghatáki), νερο – νεράκι (neró-neráki)
Do it yourself
Now try to think how would you form the following words into a diminutive: Κώστας, ποτήρι, Γιάννα, δέντρο, νονός, γιαγιά, κούκλα.