el
the (singular masculine)
la
the (singular feminine)
los
the (plural masculine)
las
the (plural feminine)
un
a/an (singular masculine)
una
a/an (singular feminine)
unos
some (masculine plural)
unas
some (feminine plural)
What happens when the noun of a sentence is feminine and starts with a stressed “a” or “ha”?
The article is switched to masculine for phonetic reasons, but the noun remains feminine. (El agua fría) (El hacha afilada)
When should “lo” be used?
“lo” is a neutral article, so it should be used with adjectives or past participles to express abstract concepts or qualities. (Lo bueno [The good thing]) (Lo importante [The important thing])