Minor grammar fixes (#728)

Co-authored-by: Benjie Gillam <benjie@jemjie.com>

Author: lorensr

spec/Section 2 -- Language.md

@@ -35,7 +35,7 @@ only valid if not followed by a character in its lookahead restriction.
 
 For example, an {IntValue} has the restriction {[lookahead != Digit]}, so cannot
 be followed by a {Digit}. Because of this, the sequence {`123`} cannot represent
-as the tokens ({`12`}, {`3`}) since {`12`} is followed by the {Digit} {`3`} and
+the tokens ({`12`}, {`3`}) since {`12`} is followed by the {Digit} {`3`} and
 so must only represent a single token. Use {WhiteSpace} or other {Ignored}
 between characters to represent multiple tokens.
 
@@ -102,7 +102,7 @@ text, any amount may appear before or after any other token and have no
 significance to the semantic meaning of a GraphQL Document. Line
 terminators are not found within any other token.
 
-Note: Any error reporting which provide the line number in the source of the
+Note: Any error reporting which provides the line number in the source of the
 offending syntax should use the preceding amount of {LineTerminator} to produce
 the line number.
 
@@ -986,7 +986,7 @@ field vs not altering a field, respectively. Neither form may be used for an
 input expecting a Non-Null type.
 
 Note: The same two methods of representing the lack of a value are possible via
-variables by either providing the a variable value as {null} and not providing
+variables by either providing the variable value as {null} or not providing
 a variable value at all.
 
 

spec/Section 3 -- Type System.md

@@ -1773,7 +1773,7 @@ include `_` in their name). For example, a custom directive used by Facebook's
 GraphQL service should be named `@fb_auth` instead of `@auth`. This is
 especially recommended for proposed additions to this specification which can
 change during the [RFC process](https://github.com/graphql/graphql-spec/blob/master/CONTRIBUTING.md).
-For example an work in progress version of `@live` should be named `@rfc_live`.
+For example a work in progress version of `@live` should be named `@rfc_live`.
 
 Directives must only be used in the locations they are declared to belong in.
 In this example, a directive is defined which can be used to annotate a field:

spec/Section 5 -- Validation.md

@@ -21,7 +21,7 @@ point in time.
 
 **Type system evolution**
 
-As GraphQL type system schema evolve over time by adding new types and new
+As GraphQL type system schema evolves over time by adding new types and new
 fields, it is possible that a request which was previously valid could later
 become invalid. Any change that can cause a previously valid request to become
 invalid is considered a *breaking change*. GraphQL services and schema
@@ -694,7 +694,7 @@ extend type Query {
 }
 ```
 
-Order does not matter in arguments. Therefore both the following example are valid.
+Order does not matter in arguments. Therefore both the following examples are valid.
 
 ```graphql example
 fragment multipleArgs on Arguments {
@@ -1245,7 +1245,7 @@ fragment dogOrHumanFragment on DogOrHuman {
 }
 ```
 
-is consider valid because {Dog} implements interface {Pet} and is a
+is considered valid because {Dog} implements interface {Pet} and is a
 member of {DogOrHuman}.
 
 However
@@ -1920,7 +1920,7 @@ query intCannotGoIntoBoolean($intArg: Int) {
 }
 ```
 
-${intArg} typed as {Int} cannot be used as a argument to {booleanArg}, typed as {Boolean}.
+${intArg} typed as {Int} cannot be used as an argument to {booleanArg}, typed as {Boolean}.
 
 List cardinality must also be the same. For example, lists cannot be passed into singular
 values.
@@ -1992,7 +1992,7 @@ In the example below, an optional variable `$booleanArg` is allowed to be used
 in the non-null argument (`nonNullBooleanArg`) because the variable provides
 a default value in the query. This behavior is explicitly supported for
 compatibility with earlier editions of this specification. GraphQL authoring
-tools may wish to report this is a warning with the suggestion to replace
+tools may wish to report this as a warning with the suggestion to replace
 `Boolean` with `Boolean!` to avoid ambiguity.
 
 ```graphql example
@@ -2003,5 +2003,5 @@ query booleanArgQueryWithDefault($booleanArg: Boolean = true) {
 }
 ```
 
-Note: The value {null} could still be provided to a such a variable at runtime.
+Note: The value {null} could still be provided to such a variable at runtime.
 A non-null argument must produce a field error if provided a {null} value.

spec/Section 6 -- Execution.md

@@ -683,7 +683,7 @@ ResolveAbstractType(abstractType, objectValue):
 
 **Merging Selection Sets**
 
-When more than one fields of the same name are executed in parallel, their
+When more than one field of the same name is executed in parallel, their
 selection sets are merged together when completing the value in order to
 continue execution of the sub-selection sets.