The Greek sentence uses the definite η (the) and not the indefinite μια (a).
Sure, but the English sentence 'what is the lecture?' doesn't really make sense
I agree. Maybe a more proper English translation would be "What is a lecture?", as if someone was asking for the definition of the word. Τι είναι η διάλεξη; would be a fitting translation to it as well, I think. ^.^
Maybe I miss something here - the Greek is "Τι είναι η διάλεξη;", the correct translation is "What is the lecture?" (translating GR to EN on PC). I am not a native English speaker, but this sounds weird to me. I'd rather say "What is the topic of the lecture" or "What is the lecture about". From the above comments I would think that either the GR or EN should have been changed?
Yes, there is a misunderstanding in this sentences and it should be: Τι είναι "η διάλεξη";
It should be asking for the meaning of the word "διάλεξη". We will edit it. Thanks for the input.