diff --git a/book/book.tex b/book/book.tex
index 98052b39..52ecee8a 100644
--- a/book/book.tex
+++ b/book/book.tex
@@ -40,7 +40,7 @@
 \usepackage{amsmath}
 \usepackage{amsthm}
 
-% format end of chapter excercises
+% format end of chapter exercises
 \newtheoremstyle{exercise}
   {12pt}        % space above
   {12pt}        % space below
@@ -2904,7 +2904,7 @@ \chapter{Scale-free networks}
 The chapter ends with a discussion of WS and BA graphs as explanatory
 models for small world networks.
 
-The code for this chapter is in {\tt chap04.ipynb} in the respository
+The code for this chapter is in {\tt chap04.ipynb} in the repository
 for this book.  More information about working with the code is
 in Section~\ref{code}.
 
diff --git a/code/chap09soln.ipynb b/code/chap09soln.ipynb
index 79141d25..15b79df2 100644
--- a/code/chap09soln.ipynb
+++ b/code/chap09soln.ipynb
@@ -109692,7 +109692,7 @@
     "# In some runs, the average vision increases at first, \n",
     "# and then falls gradually, which is surprising.\n",
     "\n",
-    "# I conjecture that the intial die-off creates pressure\n",
+    "# I conjecture that the initial die-off creates pressure\n",
     "# that kills agents that would have survived in steady state.\n",
     "\n",
     "# After the initial die-off, these agents are able to make \n",
diff --git a/code/fof_model.ipynb b/code/fof_model.ipynb
index 52ef4741..2733f393 100644
--- a/code/fof_model.ipynb
+++ b/code/fof_model.ipynb
@@ -68,7 +68,7 @@
     "\n",
     "I propose a new model that generates graphs with\n",
     "\n",
-    "1.  Low path lenths,\n",
+    "1.  Low path lengths,\n",
     "2.  Clustering coefficients similar to the HK model (but still lower than observed values), and\n",
     "3.  A degree distribution that fits observed data well.\n",
     "\n",
diff --git a/code/nkmodel.ipynb b/code/nkmodel.ipynb
index 85a71aad..64d5e1e9 100644
--- a/code/nkmodel.ipynb
+++ b/code/nkmodel.ipynb
@@ -1233,7 +1233,7 @@
     "    \n",
     "    returns: Cdf of component (neutral network) sizes,\n",
     "             float fraction of locations in a common network,\n",
-    "             float maximum fitness acheived by the agents\n",
+    "             float maximum fitness achieved by the agents\n",
     "    \"\"\"\n",
     "    nkqland = NKqLandscape(N, K, F=F)\n",
     "    \n",
diff --git a/code/nkmodelsoln.ipynb b/code/nkmodelsoln.ipynb
index 4072eab7..faf7cb73 100644
--- a/code/nkmodelsoln.ipynb
+++ b/code/nkmodelsoln.ipynb
@@ -1636,7 +1636,7 @@
     "    \n",
     "    returns: Cdf of component (neutral network) sizes,\n",
     "             float fraction of locations in a common network,\n",
-    "             float maximum fitness acheived by the agents\n",
+    "             float maximum fitness achieved by the agents\n",
     "    \"\"\"\n",
     "    nkqland = NKqLandscape(N, K, F=F)\n",
     "    \n",
diff --git a/code/sspile.ipynb b/code/sspile.ipynb
index 5a526817..5d2d12d2 100644
--- a/code/sspile.ipynb
+++ b/code/sspile.ipynb
@@ -198,7 +198,7 @@
     "from scipy.ndimage import imread\n",
     "\n",
     "def read_pile(k):\n",
-    "    \"\"\"Reads an image of a single souce sand pile model.\n",
+    "    \"\"\"Reads an image of a single source sand pile model.\n",
     "    \n",
     "    Images generated by Wesley Pegden,\n",
     "    available from http://math.cmu.edu/~wes/piles/\n",