The correct spelling is ντύνονται
This is how the verb is conjugated:
Present Tense - Passive
εγώ ντύνομαι = I am getting dressed
εσύ ντύνεσαι = you are getting dressed
αυτός ντύνεται = he is getting dressed
εμείς ντυνόμαστε = we are getting dressed
εσείς ντύνεστε = you are getting dressed
αυτοί ντύνονται = they are getting dressed
In simple words, if a verb in Present Tense ends with the sound ε, it is spelled with αι, except for the first plural and second plural form. These two forms are spelled with ε.
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Vasiliki Baskou, Instructor/Director, https://learn-greek-online.com.