In English, you use the articles the and a or an without caring whether a singular or plural noun comes after it. However, with Spanish articles, you point out whether you're referring to one or several things by making the article plural, too.
In Spanish, you have four different ways to say the:
el (ehl) (masculine singular)
la (lah) (feminine singular)
los (lohs) (masculine plural)
las (lahs) (feminine plural)
And, you have four ways to say a or an:
un (oon) (masculine a or an)
una (oo-nah) (feminine a or an)
unos (oo-nohs) (the plural of un)
unas (oo-nahs) (the plural of una)
When you make a singular noun plural, not only do you have to change the noun itself, but you have to change the article as well.
Spanish is a melodious language. It forms some plural nouns by adding an s (like English does), but it doesn’t like to have two consonants at the end of a word, so some plural nouns require inserting a vowel between an end consonant and the s. Thus, when a noun ends in a consonant, Spanish inserts an e before adding the s to turn it into a plural. Following are some examples:
el pan (ehl pahn) (the bread)
los panes (lohs pah-nehs) (the breads)
una mujer (oo-nah moo-Hehr) (a woman)
unas mujeres (oo-nahs moo-Hehr-ehs) (some women)
el canal (ehl kah-nahl) (the channel)
los canales (lohs kah-nah-lehs) (the channels)
un doctor (oon dohk-tohr) (a doctor)
unos doctores (oo-nohs dohk-toh-rehs) (some doctors)
Other nouns form plurals normally — simply add s to the noun and switch the article. Here are some examples:
el niño (ehl nee-nyo) (the boy)
los niños (lohs nee-nyohs) (the boys)
la niña (lah nee-nyah) (the girl)
las niñas (lahs nee-nyahs) (the girls)
un hombre (oon ohm-bvreh) (a man)
unos hombres (oo-nohs ohm-bvrehs) (some men)
una casa (oo-nah kah-sah) (a house)
unas casas (oo-nahs kah-sahs) (some houses)
el vino (ehl bvee-noh) (the wine)
los vinos (lohs bvee-nohs) (the wines)
el camino (ehl kah-mee-noh) (the road)
los caminos (lohs kah-mee-nohs) (the roads)
un auto (oon ahoo-toh) (a car)
unos autos (oo-nohs ahoo-tohs) (some cars)