diff --git a/py/modcmath.c b/py/modcmath.c
index 6fdd1f77b7..a147a754b8 100644
--- a/py/modcmath.c
+++ b/py/modcmath.c
@@ -68,7 +68,7 @@ mp_obj_t mp_cmath_polar(mp_obj_t z_obj) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_cmath_polar_obj, mp_cmath_polar);
 
 /// \function rect(r, phi)
-/// Returns the complex number with modules `r` and phase `phi`.
+/// Returns the complex number with modulus `r` and phase `phi`.
 mp_obj_t mp_cmath_rect(mp_obj_t r_obj, mp_obj_t phi_obj) {
     mp_float_t r = mp_obj_get_float(r_obj);
     mp_float_t phi = mp_obj_get_float(phi_obj);
@@ -77,6 +77,7 @@ mp_obj_t mp_cmath_rect(mp_obj_t r_obj, mp_obj_t phi_obj) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(mp_cmath_rect_obj, mp_cmath_rect);
 
 /// \function exp(z)
+/// Return the exponential of `z`.
 mp_obj_t mp_cmath_exp(mp_obj_t z_obj) {
     mp_float_t real, imag;
     mp_obj_get_complex(z_obj, &real, &imag);
@@ -86,6 +87,7 @@ mp_obj_t mp_cmath_exp(mp_obj_t z_obj) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_cmath_exp_obj, mp_cmath_exp);
 
 /// \function log(z)
+/// Return the natural logarithm of `z`.  The branch cut is along the negative real axis.
 // TODO can take second argument, being the base
 mp_obj_t mp_cmath_log(mp_obj_t z_obj) {
     mp_float_t real, imag;
@@ -95,6 +97,7 @@ mp_obj_t mp_cmath_log(mp_obj_t z_obj) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_cmath_log_obj, mp_cmath_log);
 
 /// \function log10(z)
+/// Return the base-10 logarithm of `z`.  The branch cut is along the negative real axis.
 mp_obj_t mp_cmath_log10(mp_obj_t z_obj) {
     mp_float_t real, imag;
     mp_obj_get_complex(z_obj, &real, &imag);
@@ -103,6 +106,7 @@ mp_obj_t mp_cmath_log10(mp_obj_t z_obj) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_cmath_log10_obj, mp_cmath_log10);
 
 /// \function sqrt(z)
+/// Return the square-root of `z`.
 mp_obj_t mp_cmath_sqrt(mp_obj_t z_obj) {
     mp_float_t real, imag;
     mp_obj_get_complex(z_obj, &real, &imag);
@@ -113,6 +117,7 @@ mp_obj_t mp_cmath_sqrt(mp_obj_t z_obj) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_cmath_sqrt_obj, mp_cmath_sqrt);
 
 /// \function cos(z)
+/// Return the cosine of `z`.
 mp_obj_t mp_cmath_cos(mp_obj_t z_obj) {
     mp_float_t real, imag;
     mp_obj_get_complex(z_obj, &real, &imag);
@@ -121,6 +126,7 @@ mp_obj_t mp_cmath_cos(mp_obj_t z_obj) {
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mp_cmath_cos_obj, mp_cmath_cos);
 
 /// \function sin(z)
+/// Return the sine of `z`.
 mp_obj_t mp_cmath_sin(mp_obj_t z_obj) {
     mp_float_t real, imag;
     mp_obj_get_complex(z_obj, &real, &imag);