Wei

Definition

A ‘wei’ refers to the smallest denomination of ether (ETH).

Understanding the Term

One wei (pronounced: “way”) is the smallest fraction of ether. Ether is a cryptocurrency token upon which the Ethereum network is based.  That is to say:

 1 wei = one quintillionth of ether (ETH)

Therefore,

                                          1 ETH = 1×10¹⁸ wei

Takeaway

A wei is to ether as a satoshi is to Bitcoin — both units are the smallest unit from which a user may make a transaction.