The term adulthood refers to the period or stage of life when an individual is considered a mature, independent adult. This typically begins in early adulthood, around the age of 18-25 years old, and continues throughout one's lifetime. During this time, individuals are expected to take on responsibilities such as holding down a job, being financially independent, forming stable relationships, and making important life decisions. Adulthood is often associated with increased independence, self-reliance, and personal autonomy.