For purposes of this subtitle, the term “partner” means a member of a partnership. In the case of a capital interest in a partnership in which capital is a material income-producing factor, whether a person is a partner with respect to such interest shall be determined without regard to whether such interest was derived by gift from any other person.
For purposes of this subchapter, a partnership agreement includes any modifications of the partnership agreement made prior to, or at, the time prescribed by law for the filing of the partnership return for the taxable year (not including extensions) which are agreed to by all the partners, or which are adopted in such other manner as may be provided by the partnership agreement.
For purposes of this subchapter, the term “liquidation of a partner’s interest” means the termination of a partner’s entire interest in a partnership by means of a distribution, or a series of distributions, to the partner by the partnership.
For rules in the case of the sale, exchange, liquidation, or reduction of a partner’s interest, see sections 704(b) and 706(c)(2).