"The poetry is a genre of literature."
Translation:Η ποίηση είναι μία κατηγορία της λογοτεχνίας.
Note that this is not merely a spelling difference but corresponds to a difference in pronunciation.
μια (no accent) has no accent because it's one syllable, and one-syllable words are generally written without accents. It's pronounced roughly [mja] or a bit as if spelled "mya" in English (with "y" as in "yes", not as in "by"), or perhaps like "mnya"
μία (with accent) has an accent because it has more than one syllable: it's [mia] with two separate vowels, or roughly "mee-ah".