There are 2 main definitions of September in English:

September1

Syllabification: Sep·tem·ber
Pronunciation: /sepˈtembər
 
/

noun

The ninth month of the year, in the northern hemisphere usually considered the first month of autumn: sow the plants in early September [as modifier]: a warm September evening
More example sentences
  • All staff have been fired with immediate effect and may not be paid for the month of September.
  • For its September concert this year the group has looked to a newer generation of musicals.
  • From September the plants start to enter dormancy so that by late October it is at a maximum.

Origin

late Old English, from Latin, from septem 'seven' (being originally the seventh month of the Roman year).

Definition of September in: