=El= before a masculine[7] noun singular
=La= " feminine[7] " "
[Footnote 7: Spanish nouns are all masculine or feminine. There are no neuter nouns.]
as—
El hombre (the man)—La mujer (the woman)
El libro (the book)—La pluma (the pen)
El recibo (the receipt)—La cuenta (the account)
=Los= before a masculine noun plural
=Las= " feminine " "
as—
Los muchachos (the boys)—Las señoras (the ladies)
Los géneros (the goods)—Las facturas (the invoices)
Los lápices (the pencils)—Las cartas (the letters).
The =Indefinite Article= is—
=Un= before a masculine noun singular
=Una= " feminine " "