diff --git a/src/backend/access/gist/gistbuild.c b/src/backend/access/gist/gistbuild.c
index 3dc3e96df4..988896d289 100644
--- a/src/backend/access/gist/gistbuild.c
+++ b/src/backend/access/gist/gistbuild.c
@@ -248,7 +248,7 @@ gistValidateBufferingOption(char *value)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 				 errmsg("invalid value for \"buffering\" option"),
-			   errdetail("Valid values are \"on\", \"off\" and \"auto\".")));
+			   errdetail("Valid values are \"on\", \"off\", and \"auto\".")));
 	}
 }
 
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index a81f7c76c3..fcb087ed15 100644
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -739,7 +739,7 @@ AtPrepare_Notify(void)
 	if (pendingActions || pendingNotifies)
 		ereport(ERROR,
 				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("cannot PREPARE a transaction that has executed LISTEN, UNLISTEN or NOTIFY")));
+				 errmsg("cannot PREPARE a transaction that has executed LISTEN, UNLISTEN, or NOTIFY")));
 }
 
 /*
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 07dc326cea..28889c1f44 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -2115,7 +2115,7 @@ renameatt_check(Oid myrelid, Form_pg_class classform, bool recursing)
 		relkind != RELKIND_FOREIGN_TABLE)
 		ereport(ERROR,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is not a table, view, composite type, index or foreign table",
+				 errmsg("\"%s\" is not a table, view, composite type, index, or foreign table",
 						NameStr(classform->relname))));
 
 	/*
diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
index a83b52ea29..56229cb4df 100644
--- a/src/backend/libpq/hba.c
+++ b/src/backend/libpq/hba.c
@@ -1391,7 +1391,7 @@ parse_hba_auth_opt(char *name, char *val, HbaLine *hbaline, int line_num)
 			hbaline->auth_method != uaGSS &&
 			hbaline->auth_method != uaSSPI &&
 			hbaline->auth_method != uaCert)
-			INVALID_AUTH_OPTION("map", gettext_noop("ident, peer, krb5, gssapi, sspi and cert"));
+			INVALID_AUTH_OPTION("map", gettext_noop("ident, peer, krb5, gssapi, sspi, and cert"));
 		hbaline->usermap = pstrdup(val);
 	}
 	else if (strcmp(name, "clientcert") == 0)
@@ -1510,7 +1510,7 @@ parse_hba_auth_opt(char *name, char *val, HbaLine *hbaline, int line_num)
 		if (hbaline->auth_method != uaKrb5 &&
 			hbaline->auth_method != uaGSS &&
 			hbaline->auth_method != uaSSPI)
-			INVALID_AUTH_OPTION("krb_realm", gettext_noop("krb5, gssapi and sspi"));
+			INVALID_AUTH_OPTION("krb_realm", gettext_noop("krb5, gssapi, and sspi"));
 		hbaline->krb_realm = pstrdup(val);
 	}
 	else if (strcmp(name, "include_realm") == 0)
@@ -1518,7 +1518,7 @@ parse_hba_auth_opt(char *name, char *val, HbaLine *hbaline, int line_num)
 		if (hbaline->auth_method != uaKrb5 &&
 			hbaline->auth_method != uaGSS &&
 			hbaline->auth_method != uaSSPI)
-			INVALID_AUTH_OPTION("include_realm", gettext_noop("krb5, gssapi and sspi"));
+			INVALID_AUTH_OPTION("include_realm", gettext_noop("krb5, gssapi, and sspi"));
 		if (strcmp(val, "1") == 0)
 			hbaline->include_realm = true;
 		else
diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index 245030f531..ca0042a176 100644
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -2750,7 +2750,7 @@ width_bucket_float8(PG_FUNCTION_ARGS)
 	if (isnan(operand) || isnan(bound1) || isnan(bound2))
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_ARGUMENT_FOR_WIDTH_BUCKET_FUNCTION),
-			  errmsg("operand, lower bound and upper bound cannot be NaN")));
+			  errmsg("operand, lower bound, and upper bound cannot be NaN")));
 
 	/* Note that we allow "operand" to be infinite */
 	if (isinf(bound1) || isinf(bound2))
diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index cee6cab954..627870a446 100644
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -1223,7 +1223,7 @@ width_bucket_numeric(PG_FUNCTION_ARGS)
 		NUMERIC_IS_NAN(bound2))
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_ARGUMENT_FOR_WIDTH_BUCKET_FUNCTION),
-			  errmsg("operand, lower bound and upper bound cannot be NaN")));
+			  errmsg("operand, lower bound, and upper bound cannot be NaN")));
 
 	init_var(&result_var);
 	init_var(&count_var);
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 84b330c6d3..a5becbe8ff 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2240,7 +2240,7 @@ static struct config_int ConfigureNamesInt[] =
 	},
 	{
 		{"autovacuum_analyze_threshold", PGC_SIGHUP, AUTOVACUUM,
-			gettext_noop("Minimum number of tuple inserts, updates or deletes prior to analyze."),
+			gettext_noop("Minimum number of tuple inserts, updates, or deletes prior to analyze."),
 			NULL
 		},
 		&autovacuum_anl_thresh,
@@ -2494,7 +2494,7 @@ static struct config_real ConfigureNamesReal[] =
 	},
 	{
 		{"autovacuum_analyze_scale_factor", PGC_SIGHUP, AUTOVACUUM,
-			gettext_noop("Number of tuple inserts, updates or deletes prior to analyze as a fraction of reltuples."),
+			gettext_noop("Number of tuple inserts, updates, or deletes prior to analyze as a fraction of reltuples."),
 			NULL
 		},
 		&autovacuum_anl_scale,
diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index aabbdac8d0..b39d2e7bf3 100644
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -1245,7 +1245,7 @@ main(int argc, char **argv)
 					streamwal = true;
 				else
 				{
-					fprintf(stderr, _("%s: invalid xlog option \"%s\", must be empty, \"fetch\" or \"stream\"\n"),
+					fprintf(stderr, _("%s: invalid xlog option \"%s\", must be empty, \"fetch\", or \"stream\"\n"),
 							progname, optarg);
 					exit(1);
 				}
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index c3c861d857..d845c90ac8 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -817,7 +817,7 @@ help(const char *progname)
 	printf(_("  --no-tablespaces            do not dump tablespace assignments\n"));
 	printf(_("  --no-unlogged-table-data    do not dump unlogged table data\n"));
 	printf(_("  --quote-all-identifiers     quote all identifiers, even if not key words\n"));
-	printf(_("  --section=SECTION           dump named section (pre-data, data or post-data)\n"));
+	printf(_("  --section=SECTION           dump named section (pre-data, data, or post-data)\n"));
 	printf(_("  --serializable-deferrable   wait until the dump can run without anomalies\n"));
 	printf(_("  --use-set-session-authorization\n"
 			 "                              use SET SESSION AUTHORIZATION commands instead of\n"
diff --git a/src/bin/pg_dump/pg_restore.c b/src/bin/pg_dump/pg_restore.c
index 1c026cf91a..b5f4c627c4 100644
--- a/src/bin/pg_dump/pg_restore.c
+++ b/src/bin/pg_dump/pg_restore.c
@@ -463,7 +463,7 @@ usage(const char *progname)
 			 "                           created\n"));
 	printf(_("  --no-security-labels     do not restore security labels\n"));
 	printf(_("  --no-tablespaces         do not restore tablespace assignments\n"));
-	printf(_("  --section=SECTION        restore named section (pre-data, data or post-data)\n"));
+	printf(_("  --section=SECTION        restore named section (pre-data, data, or post-data)\n"));
 	printf(_("  --use-set-session-authorization\n"
 			 "                           use SET SESSION AUTHORIZATION commands instead of\n"
 	  "                           ALTER OWNER commands to set ownership\n"));
diff --git a/src/test/regress/expected/numeric.out b/src/test/regress/expected/numeric.out
index 71c520e5e7..94cb0ed551 100644
--- a/src/test/regress/expected/numeric.out
+++ b/src/test/regress/expected/numeric.out
@@ -746,9 +746,9 @@ ERROR:  count must be greater than zero
 SELECT width_bucket(3.5::float8, 3.0::float8, 3.0::float8, 888);
 ERROR:  lower bound cannot equal upper bound
 SELECT width_bucket('NaN', 3.0, 4.0, 888);
-ERROR:  operand, lower bound and upper bound cannot be NaN
+ERROR:  operand, lower bound, and upper bound cannot be NaN
 SELECT width_bucket(0::float8, 'NaN', 4.0::float8, 888);
-ERROR:  operand, lower bound and upper bound cannot be NaN
+ERROR:  operand, lower bound, and upper bound cannot be NaN
 -- normal operation
 CREATE TABLE width_bucket_test (operand_num numeric, operand_f8 float8);
 COPY width_bucket_test (operand_num) FROM stdin;