Principal zero-coupon bonds that have been converted from paper to an electronic form. The term is often used in conjunction with written materials on bond mutual funds. The significance of the conversion is that the bonds can be wire transferred instead of physically delivered. The U.S. Department of the Treasury’s Bureau of the Public Debt (BPD) also lets holders of the principal portions, or corpora, of U.S. Treasury bearer securities that have been stripped of some or all of their non-callable coupons to have an opportunity to convert their stripped corpora to book-entry form by using the Bearer Corpora Conversion System. Keeping the Treasuries in book-entry form makes them easier to transfer.