The difference between Mature and Young

When used as verbs, mature means to become mature, whereas young means to become or seem to become younger.

When used as adjectives, mature means fully developed, whereas young means in the early part of growth or life.

Young is also noun with the meaning: people who are young.

check bellow for the other definitions of Mature and Young

Mature as an adjective:

Fully developed; grown up in terms of physical appearance, behaviour or thinking; ripe.

Examples:

"She is quite mature for her age."
Mature as an adjective:

Brought to a state of complete readiness.

Examples:

"a mature plan"
Mature as an adjective:

Profound; careful.

Examples:

"The headmaster decided to expel the boy after a mature consideration."
Mature as an adjective (medicine, obsolete):

Come to, or in a state of, completed suppuration.

Mature as a verb (intransitive, of food, especially fruit):

To become mature; to ripen.
Mature as a verb (intransitive):

To gain experience or wisdom with age.
Mature as a verb (transitive):

To make something mature.
Mature as a verb (intransitive, finance):

To reach the date when payment is due

Young as an adjective:

In the early part of growth or life; born not long ago.

Examples:

"a lamb is a young sheep; these picture books are for young readers"
Young as an adjective:

At an early stage of existence or development; having recently come into existence.

Examples:

"the age of space travel is still young; a young business"
Young as an adjective:

(Not) advanced in age; (far towards or) at a specified stage of existence or age.

Examples:

"How young is your dog? Her grandmother turned 70 years young last month."
Young as an adjective:

Junior (of two related people with the same name).
Young as an adjective:

(of a decade of life) Early.
Young as an adjective:

Youthful; having the look or qualities of a young person.

Examples:

"My grandmother is a very active woman and is quite young for her age."
Young as an adjective:

Of or belonging to the early part of life.

Examples:

"The cynical world soon shattered my young dreams."
Young as an adjective (obsolete):

Having little experience; inexperienced; unpracticed; ignorant; weak.

Young as a noun:

People who are young; young people, collectively; youth.

Examples:

"The young of today are well-educated."
Young as a noun:

Young or immature offspring (especially of an animal).

Examples:

"The lion caught a gnu to feed its young."

"The lion's young are curious."
Young as a noun (rare, possibly, nonstandard):

An individual offspring; a single recently born or hatched organism.

Young as a verb (informal, or, demography):

To become or seem to become younger.
Young as a verb (informal, or, demography):

To cause to appear younger.
Young as a verb (geology):

To exhibit younging.