diff --git a/book/pages/phase_shifters_pn.ipynb b/book/pages/phase_shifters_pn.ipynb
index 1894814..0defffa 100644
--- a/book/pages/phase_shifters_pn.ipynb
+++ b/book/pages/phase_shifters_pn.ipynb
@@ -84,7 +84,7 @@
    "cell_type": "markdown",
    "metadata": {},
    "source": [
-    "PIN phase shifters, like PN junction phase shifters, also operate based on the plasma dispersion effect. Like the PN junction phase shifter, a PIN phase shifter includes a P-doped region and an N-doped region, but the material between the two doped regions is undoped. This undoped region, also called the \"intrinsic\" region, copmrises the width of the waveguide that the photonic signal travels through. The added material of the intrinsic region helps to offset some of the optical loss experienced by PN junction phase shifters, at the cost of slightly increasing the time constant of the device. "
+    "PIN phase shifters, like PN junction phase shifters, also operate based on the plasma dispersion effect. Like the PN junction phase shifter, a PIN phase shifter includes a P-doped region and an N-doped region, but the material between the two doped regions is undoped. This undoped region, also called the \"intrinsic\" region, comprises the width of the waveguide that the photonic signal travels through. The added material of the intrinsic region helps to offset some of the optical loss experienced by PN junction phase shifters, at the cost of slightly increasing the time constant of the device. "
    ]
   },
   {