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"Younger" is a form of "younger", an adjective which is often translated as "menor". "Young" is an adjective which is often translated as "joven". Learn more about the difference between "younger" and "young" below.
younger(
yuhng
-
guhr
)An adjective is a word that describes a noun (e.g., the big dog).
a. menor 
My younger brother just graduated from college.Mi hermano menor acaba de graduarse de la universidad.
b. más joven 
Ana Maria was two years younger than her boyfriend.Ana María era dos años más joven que su novio.
c. más chico 
Daniel is younger than the other students in his grade.Daniel es más chico que los demás alumnos de su curso.
An adverb is a word that describes a verb, an adjective, or other adverbs (e.g., to run quickly, very tired).
a.  no direct translation
This refers to an idiomatic word or phrase for which there is no word-for-word translation.
Ian acts younger than he is because his parents spoil him.Ian se comporta como un niño más chiquito de lo que es porque sus padres lo miman.
Marieta is sometimes mistaken for her daughter over the phone because she sounds younger than she actually is.A veces confunden a Marieta con su hija en el teléfono porque suena más joven de lo que realmente es.
young(
yuhng
)An adjective is a word that describes a noun (e.g., the big dog).
1. (age)
a. joven 
My mother and father married at a young age.Mi madre y padre se casaron cuando eran jóvenes.
2. (appearance)
a. verde 
My assistant is still young at this, but he'll get better.Mi asistente todavía está muy verde, pero ya mejorará.
A plural noun indicates that there is more than one person, place, thing, or idea.
a. la gente joven (F)
(f) means that a noun is feminine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
The young are full of hope.La gente joven está llena de esperanza.
b. los jóvenes (M)
(m) means that a noun is masculine. Spanish nouns have a gender, which is either feminine (like la mujer or la luna) or masculine (like el hombre or el sol).
The elderly always complain about the young, and vice versa.Los viejos siempre se quejan de los jóvenes, y vice versa.