diff --git a/src/engine/engine_support.h b/src/engine/engine_support.h
index cab2f4bc..203a8478 100644
--- a/src/engine/engine_support.h
+++ b/src/engine/engine_support.h
@@ -146,7 +146,7 @@ MJAPI void mj_differentiatePos(const mjModel* m, mjtNum* qvel, mjtNum dt,
 // integrate position with given velocity
 MJAPI void mj_integratePos(const mjModel* m, mjtNum* qpos, const mjtNum* qvel, mjtNum dt);
 
-// normalize all quaterions in qpos-type vector
+// normalize all quaternions in qpos-type vector
 MJAPI void mj_normalizeQuat(const mjModel* m, mjtNum* qpos);
 
 // map from body local to global Cartesian coordinates
diff --git a/src/engine/engine_util_spatial.h b/src/engine/engine_util_spatial.h
index 0b2d1395..f7babb85 100644
--- a/src/engine/engine_util_spatial.h
+++ b/src/engine/engine_util_spatial.h
@@ -47,13 +47,13 @@ MJAPI void mju_subQuat(mjtNum res[3], const mjtNum qa[4], const mjtNum qb[4]);
 // convert quaternion to 3D rotation matrix
 MJAPI void mju_quat2Mat(mjtNum res[9], const mjtNum quat[4]);
 
-// convert 3D rotation matrix to quaterion
+// convert 3D rotation matrix to quaternion
 MJAPI void mju_mat2Quat(mjtNum quat[4], const mjtNum mat[9]);
 
 // time-derivative of quaternion, given 3D rotational velocity
 MJAPI void mju_derivQuat(mjtNum res[4], const mjtNum quat[4], const mjtNum vel[3]);
 
-// integrate quaterion given 3D angular velocity
+// integrate quaternion given 3D angular velocity
 MJAPI void mju_quatIntegrate(mjtNum quat[4], const mjtNum vel[3], mjtNum scale);
 
 // compute quaternion performing rotation from z-axis to given vector