diff --git a/13/2d-fbm.frag b/13/2d-fbm.frag
index d4fdfca..aeb9f7f 100644
--- a/13/2d-fbm.frag
+++ b/13/2d-fbm.frag
@@ -38,14 +38,14 @@ float noise (in vec2 st) {
 float fbm (in vec2 st) {
     // Initial values
     float value = 0.0;
-    float amplitud = .5;
+    float amplitude = .5;
     float frequency = 0.;
     //
     // Loop of octaves
     for (int i = 0; i < OCTAVES; i++) {
-        value += amplitud * noise(st);
+        value += amplitude * noise(st);
         st *= 2.;
-        amplitud *= .5;
+        amplitude *= .5;
     }
     return value;
 }
diff --git a/13/README-ch.md b/13/README-ch.md
index 4316bfb..d239c44 100644
--- a/13/README-ch.md
+++ b/13/README-ch.md
@@ -80,7 +80,7 @@ for (int i = 0; i < octaves; i++) {
 for (int i = 0; i < OCTAVES; i++) {
     value += amplitude * abs(snoise(st));
     st *= 2.;
-    amplitud *= .5;
+    amplitude *= .5;
 }
 ```
 
diff --git a/13/README.md b/13/README.md
index aad318c..47beb52 100644
--- a/13/README.md
+++ b/13/README.md
@@ -11,7 +11,7 @@ y = amplitude * sin(x * frequency);
 "></div>
 
 * Try changing the values of the frequency and amplitude to understand how they behave.
-* Using shaping functions, try changing the amplitud over time.
+* Using shaping functions, try changing the amplitude over time.
 * Using shaping functions, try changing the frequency over time.
 
 By doing the last two exercises you have managed to "modulate" a sine wave, and you just created AM (amplitude modulated) and FM (frequency modulated) waves. Congratulations!
@@ -80,7 +80,7 @@ Using more or less the same technique, it's also possible to obtain other effect
 for (int i = 0; i < OCTAVES; i++) {
     value += amplitude * abs(snoise(st));
     st *= 2.;
-    amplitud *= .5;
+    amplitude *= .5;
 }
 ```
 
diff --git a/13/turbulence.frag b/13/turbulence.frag
index 7478a56..2bc4e49 100644
--- a/13/turbulence.frag
+++ b/13/turbulence.frag
@@ -87,14 +87,14 @@ float snoise(vec2 v) {
 float turbulence (in vec2 st) {
     // Initial values
     float value = 0.0;
-    float amplitud = .5;
+    float amplitude = .5;
     float frequency = 0.;
     //
     // Loop of octaves
     for (int i = 0; i < OCTAVES; i++) {
-        value += amplitud * abs(snoise(st));
+        value += amplitude * abs(snoise(st));
         st *= 2.;
-        amplitud *= .5;
+        amplitude *= .5;
     }
     return value;
 }