Aave (from the Finnish word for "ghost") is an open source non-custodial protocol on Ethereum for decentralized lending and borrowing. For lenders, the protocol mints ERC20-compliant aTokens at a 1:1 ratio to supplied assets. Interest immediately starts compounding continuously, represented by a steady increase in the amount of aTokens held by the lender. This interest stream may be redirected to any address, separate from the aTokens that represent the underlying principal. Aave offers flash loans: trustless, uncollateralized loans where borrowing and repayment must occur in the same transaction. Aimed at developers, this feature could lead to innovative uses of DeFi.