Dividing the lifespan [edit]
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An animal's life is often divided into various age ranges. However, because biological changes are slow-moving and can vary within one's own species, arbitrary dates are usually set to mark periods of life. The human divisions given below are not valid in all cultures:
- Juvenile (via infancy, childhood, preadolescence, adolescence): 0–19
- Early adulthood: 20–39
- Middle adulthood: 40–59
- Late adulthood: 60+
Ages can also be divided into numerical units:
| Term | Age (years, inclusive) |
|---|---|
| Denarian | 10 to 19 |
| Vicenarian | 20 to 29 |
| Tricenarian | 30 to 39 |
| Quadragenarian | 40 to 49 |
| Quinquagenarian | 50 to 59 |
| Sexagenarian | 60 to 69 |
| Septuagenarian | 70 to 79 |
| Octogenarian | 80 to 89 |
| Nonagenarian | 90 to 99 |
| Centenarian | 100 to 109 |
| Supercentenarian | 110 and older |
People from 13 to 19 years of age are also known as teens or teenagers. Tween or Twelvie is an American neologism referring to someone aged 10 through 12.[21] The casual terms "twentysomething", "thirtysomething", etc. are also in use to describe people by decades of age.
