BBO
Bhagavad-pitā As It Is
Yudhisthira—the eldest of the five Pāndava brothers...
Yuga —one of the four ages of the universe, which differ in length and which rotate like calendar months.  See also  Satya-yuga, Tretā-yuga, Dvāpara-yuga and Kali-yuga.
Yugāvatāras —the incarnations of the Lord who appear for each of the four different millenniums to prescribe the appropriate form of spiritual realization for that age.