Add Sui to glossary and note its use for currency (#1134)

* Update sui-glossary.md

* Update sui-glossary.md

Capitalizing SUI as the token

* Update sui-glossary.md

Incorporate feedback from team

* Update sui-glossary.md

* Update sui-glossary.md

Incorporating Alonso's definition for gas, adding link to Ethereum definition

doc/src/learn/sui-glossary.md

@@ -67,7 +67,7 @@ stage is considered closure for an exchange or other blockchain transaction.
 
 ### Gas
 
-As with other blockchains, [gas](https://www.investopedia.com/terms/g/gas-ethereum.asp) in Sui is the currency for the cost of conducting a transaction.
+[Gas](https://ethereum.org/en/developers/docs/gas/) refers to the computational effort required for executing operations on the Sui network. In Sui, gas is paid with the network's native currency SUI. The cost of executing a transaction in SUI units is referred to as the transaction fee.
 
 
 ### Genesis
@@ -103,6 +103,10 @@ A [smart contract](https://en.wikipedia.org/wiki/Smart_contract) is an agreement
 
 Single-writer objects are owned by one account. In Sui, transactions affecting only single-writer objects owned by the same account may proceed with only a check of the sender’s account, greatly speeding transaction times.
 
+### Sui/SUI
+
+Sui refers to the Sui blockchain, the SUI currency, and the [Sui open source project](https://github.com/MystenLabs/sui/) as a whole.
+
 
 ### Total order
 
@@ -118,4 +122,3 @@ A transfer is switching the owner address of a token to a new one via command in
 available in the wallet.
 
 For more information, see [Transferring objects](../build/wallet.md#transferring-objects).
-