minor doc fix.

docs/guide/form.md

@@ -128,10 +128,10 @@ div.required label:after {
 }
 ```
 
-Handling variable number of models with a single form
------------------------------------------------------
+Handling multiple models with a single form
+-------------------------------------------
 
-Sometimes you need to handle multiple models of the same kind in a signle form. For example, multiple settings where
+Sometimes you need to handle multiple models of the same kind in a single form. For example, multiple settings where
 each setting is stored as name-value and is represented by `Setting` model. The
 following shows how to implement it with Yii.
 
@@ -188,4 +188,4 @@ ActiveForm::end();
 ```
 
 Here for each setting we are rendering name and an input with a value. It is important to add a proper index
-to input name since that is how `loadMultiple` determines which model to fill with which values.
\ No newline at end of file
+to input name since that is how `loadMultiple` determines which model to fill with which values.