diff --git a/protocol/blockchain/script.md b/protocol/blockchain/script.md
index 48f2f64..7e6a064 100644
--- a/protocol/blockchain/script.md
+++ b/protocol/blockchain/script.md
@@ -12,4 +12,20 @@ This page will focus on how the scripts are run, what they are capable of, and w
 
 ## Script Execution
 
-Scripts are executed using a stack-based memory model.
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+Scripts are executed using a stack-based memory model and have an intentionally restricted set of available operations.  Unlike the common general-purpose programming languages your are probably aware of, Script (the term for the language itself) does not allow for loops, persistent state/memory across script executions, or the definition of functions.  Instead, scripts are expected to contain whatever data they need and use the available operations to prove transaction validity.
+
+Scripts are run when validating transactions, and successful execution of all of the scripts defined by the transaction is a necessary, but not sufficient, condition for transaction validity.  See [Transaction Validation](/protocol/blockchain/transaction-validation) for more details.
+
+As a part of validating a transaction, a script is built for each input spent by the transaction.  Each script is the concatenation of the [unlocking script](/protocol/blockchain/transaction/unlocking-script) provided with the input definition (which is used that the beginning of the script) and the locking script provided by the [previous output](/protocol/blockchain/transaction#transaction-outputs) being referenced (which is the end of the script).  The exception to this is [pay to script hash](/protocol/blockchain/transaction/locking-script#standard-scripts), which has an altered execution workflow.  In general, though, this combined unlocking/locking script is then executed and considered successful if and only if the following conditions are met:
+
+ - **Non-Zero Value** - after execution the top of the stack must contain a non-zero (TRUE) value.
+ - **No Stack Overflows** - no operation should attempt to pop a value from the stack when the stack is empty.
+ - **Clean Stack** - after execution the stack must only contain a single value, which must be non-zero (TRUE).  Added in [HF20181115](/protocol/forks/HF20181115).
+
+Additionally, in order for the combined script to be valid, the following must be true:
+
+ - **Non-Empty Scripts** - both the locking and unlocking scripts must be non-empty.
+ - **Max Script Length** - the locking and unlocking script must each be less than the max script length of 10,000 bytes (for a combined script maximum of 20,000 bytes).
+ - **Contained Control Flow** - an IF/ELSE block cannot start in the unlocking script and end in the locking script, the script must be in the top-level scope when the locking script execution begins.
+ - **Permitted Operations Only** - the locking script must not contain.
+ - **Push Only** - the unlocking script must contain only push operations (i.e. those with op codes 0x60 or less).  Added in [HF20181115](/protocol/forks/HF20181115).
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