In Spanish, nouns that start with a stressed "a" (or "ha-") are feminine, but they follow a specific rule when they are accompanied by articles and quantifiers.
With the Artículo definido
These words take the singular definite article el (not la):
This would be difficult to pronounce:
- La agua
- La ala
They are incorrect.
However it is different when using the plural definite article los/las (the plural). They DO take las (not los).
With the Artículo indefinido
With the indefinite articles un/una (= a plural), although un is more commonly used, una is also acceptable and not considered incorrect.
Both plurals unos/unas are also acceptable.
Be careful because if there is an adjective between the article and the noun, then everything is in the feminine form!
Esta agua/ Estas aguas.
Este agua/ Estos aguas.
This water/these waters.
Mucha agua/Muchas aguas.
Mucho agua/Muchos aguas.
A lot of water/lots of waters.
Nuestra agua/Nuestras aguas.
Nuestro agua/Nuestros aguas.
Our water/our waters.
The names of the letters -h- (hache) and -a- (a) are exceptions to this rule. They DO take la, (not el).
The [letter] h.
The [letter] a.
La hache y la a son dos letras del alfabeto español.
[The] aitch and [the] a are two letters in the Spanish alphabet.
Here is a list containing some common words that follow this rule: