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"Un" is an indefinite article which is often translated as "a", and "araña" is a noun which is often translated as "spider". Learn more about the difference between "un" and "araña" below.
un()
An indefinite article is a word that indicates that a noun is not specific (e.g., a girl).
1. (singular)
b. an (before vowel sound)
Tienen una vieja cámara que todavía funciona.They have an old camera which is still working.
la araña()
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
1. (animal)
2. (lamp)
a. chandelier
El hotel contaba con una gran araña con velas prendidas.The hotel had a large chandelier with lit candles.