西语经典语法：不定冠词和定冠词（西英）

 Two words for 'the': el and la

el museo the museum
el hotel the hotel
la plaza the square
la calle the street

If a noun ends in -o, it's masculine and goes with el.
If it ends in -a, it's usually feminine and goes with la.

If you look up any noun in the dictionary it'll show whether it's masculine (m) orfeminine (f) so you'll know which word for the to use:

calle (f): street
hotel (m): hotel

It's a good idea to learn the gender along with the word.

Words that go with el usually go with un; and words with la usually go with una

el parque the park
un parque a park
la calle the street
una calle a street

 

Two words for 'a': un and una

Un and una are the two Spanish words that can mean a (an) or one.
un bocadillo a roll or one roll
una tortilla an omelette or one omelette.

This is because all Spanish nouns, whether referring to people, things or ideas, are either feminine or masculine.

Una goes with the feminine nouns and un with the masculine ones.

The idea of masculine and feminine is quite logical when referring to people.

un hombre a man
una mujer a woman

For omelettes and sandwiches, it's not so obvious, although you do get used to it.

Fortunately, there's a good rule of thumb: nouns ending in -o are masculine and most of those ending in -a are feminine.