diff --git a/docs/lesson01/rpi-os.md b/docs/lesson01/rpi-os.md
index 277a30ee..798bd4b9 100644
--- a/docs/lesson01/rpi-os.md
+++ b/docs/lesson01/rpi-os.md
@@ -193,7 +193,7 @@ _start:
 ```
 
 The first thing this function does is check the processor ID. The Raspberry Pi 3 has four core processors, and after the device is powered on, each core begins to execute the same code. However, we don't want to work with four cores; we want to work only with the first one and put all of the other cores in an endless loop. This is exactly what the `_start` function is responsible for. It gets the processor ID from the [mpidr_el1](http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0500g/BABHBJCI.html) system register. 
-If the current process ID is 0, then execution is transferred to the `master` function:
+If the current processor ID is 0, then execution is transferred to the `master` function:
 
 ```
 master: