diff --git a/docs/introduction-to-smart-contracts.rst b/docs/introduction-to-smart-contracts.rst
index bfc342d97..ad0a96509 100644
--- a/docs/introduction-to-smart-contracts.rst
+++ b/docs/introduction-to-smart-contracts.rst
@@ -350,10 +350,10 @@ from its own.
 The second memory area is called **memory**, of which a contract obtains
 a freshly cleared instance for each message call. Memory is linear and can be
 addressed at byte level, but reads are limited to a width of 256 bits, while writes
-can be either 8 bits or 256 bits wide. Memory is expanded by accessing (either
-reading or writing) a previously untouched memory offset. At the time of expansion,
-the cost in gas must be paid. Memory is more costly the larger it grows (it scales
-quadratically).
+can be either 8 bits or 256 bits wide. Memory is expanded by a word (256-bit), when
+accessing (either reading or writing) a previously untouched memory word (ie. any offset
+within a word). At the time of expansion, the cost in gas must be paid. Memory is more
+costly the larger it grows (it scales quadratically).
 
 The EVM is not a register machine but a stack machine, so all
 computations are performed on an area called the **stack**. It has a maximum size of