Which One?

¡Más bonito que el rojo!
In English, we use one to avoid repeating the same word twice; for example, The blue dress is more beautiful than the red one.
In Spanish, you can do the same thing! You can put el or la before an adjective to avoid repetition. Make sure the gender matches!
¿Te gusta el vestido azul o el rojo?
Do you like the blue dress or the red one?
Esta camisa verde es más cara que la amarilla.
This green shirt is more expensive than the yellow one.
¡Más rápido que el mío!
Another way we avoid repeating nouns in English is to use words like mine and yours. For example, Your car is faster than mine.

In Spanish,
mine is el mío or la mía, and yours is el tuyo or la tuya.
Ese perro es más gordo que el mío.
That dog is fatter than mine.
Mi camisa es amarilla y la tuya es verde.
My shirt is yellow and yours is green.
Elijo este vestido
Verbs that end in ‑gir or ‑ger, like elegir or coger, have yo forms ending in ‑jo in the present tense.
Yo siempre cojo las llaves.
I always take the keys.
Notice that elegir is also a stem‑changing e‑to‑i verb!
subjectverb (elegir)
yoelijo
eliges
él / ella / ustedelige
nosotros / nosotraselegimos
ellos / ellas / ustedeseligen