This is the 942nd most frequent Turkish word.
eylül
"September."
Here, 'eylül' refers to the name of the month September.
Eylül ayında hava serinlemeye başlar.
The weather starts to cool down in September.
In this sentence, 'eylül' is used as a proper noun indicating the name of the month.
Eylül, yaprakların dökülmeye başladığı aydır.
September is the month when leaves begin to fall.
Here, 'eylül' is used as a given name for a person.