You might find this strange, but in Arabic, we have a name for every "phase" of a person's life.
Waleed (newly born)
Radhee3 (one who is breastfed)
Tifl (child)
Sabbi (older child ... I'd say someone who is 6 years +)
Ghulam (older than Sabbi, and that's probably 10+)
Fatta (I'd say between 12-17)
Shaab (young man, probably 18+)
Rajjul (man, that's like nearing or mid 30s)
Kahl (one who has reached maturity, 30+)
Shaykh or Sha'ib (one whose hair and beard has started greying indicating old age, 50+)
Mussin (60+)
Mu3ammir or Harrim (one who lives long or one who becomes old and weak, and that would be 70+)
Does that make sense?
Maybe you were asking for a simple answer, but I get carried away sometimes
