chore: fix typo at application.md (#1477)

Author: 0x009922

src/guide/essentials/application.md

@@ -120,4 +120,4 @@ const app2 = createApp({
 app2.mount('#container-2')
 ```
 
-If you are using Vue to enhance server-rendered HTML and only need Vue to control specific parts of a large page, avoid mounting a singe Vue application instance on the entire page. Instead, create multiple small application instances and mount them on the elements they are responsible for.
+If you are using Vue to enhance server-rendered HTML and only need Vue to control specific parts of a large page, avoid mounting a single Vue application instance on the entire page. Instead, create multiple small application instances and mount them on the elements they are responsible for.