§1835. Definitions
For the purpose of this Sub-part, the term "surviving income beneficiary" means a natural person designated in the trust instrument to enjoy a portion of trust income, whether presently or in the future, or even conditionally; a principal beneficiary who is designated also a beneficiary of income, whether presently or in the future, or even conditionally; and also includes a principal beneficiary who becomes entitled to enjoy income because of the termination of the rights of an income beneficiary. It does not include a beneficiary whose interest in income has terminated.