Update about.md

Author: armanh3k

concepts/nullability/about.md

@@ -2,11 +2,11 @@
 
 In Java, the [`null` literal][null-keyword] is used to denote the absence of a value.
 
-[Primitive variables][primitive-data-types] in java all have a default value and therefore can never be `null`.
+[Primitive variables][primitive-data-types] in Java all have a default value and therefore can never be `null`.
 By convention, they start with a lowercase letter e.g `int`.
 
-[Reference variables][reference-data-types] contain the memory address of an object and can have a value of null.
-These variables usually start with an uppercase e.g `String`.
+[Reference variables][reference-data-types] contain the memory address of an object and can have a value of `null`.
+They generally start with an uppercase letter, e.g. `String`.
 
 Attempting to assign a primitive variable a value of `null` will result in a compile time error as the variable always holds a default value of the type assigned.