# Repay Borrow

The repay function transfers an asset into the protocol, reducing the user's borrow balance.

**SErc20**

```
function repayBorrow(uint repayAmount) returns (uint)
```

* `msg.sender`: The account which borrowed the asset, and shall repay the borrow.
* `repayAmount`: The amount of the underlying borrowed asset to be repaid. A value of -1 (i.e. 2 ^ 256 - 1) can be used to repay the full amount.
* `RETURN`: 0 on success, otherwise an [Error code](https://docs.strike.org/stokens/error-codes)

Before repaying an asset, users must first [approve](https://eips.ethereum.org/EIPS/eip-20#approve) the sToken to access their token balance.

**SEther**

```
function repayBorrow() payable
```

* `msg.value` *\[payable]*: The amount of ether to be repaid, in wei.
* `msg.sender`: The account which borrowed the asset, and shall repay the borrow.
* `RETURN`: No return, reverts on error.

**Solidity**

```
SEther sToken = SEther(0x3FDB...);
require(sToken.repayBorrow.value(100)() == 0, "transfer approved?");
```

**Web3 1.0**

```javascript
const sToken = SErc20.at(0x3FDA...);
sToken.methods.repayBorrow(10000).send({from: ...});
```