typo

NEWS.md

@@ -29,7 +29,7 @@ BREAKING CHANGES AND DEPRECATIONS
   was also fixed now.
 
 * `demean()` (and `degroup()`) gets an `append` argument that defaults to `TRUE`,
-  to append the centered variabled to the original data frame, instead of
+  to append the centered variables to the original data frame, instead of
   returning the de- and group-meaned variables only. Use `append = FALSE` to
   for the previous default behaviour (i.e. only returning the newly created
   variables).