diff --git a/flect_test.go b/flect_test.go
index 848d77a..4ab6251 100644
--- a/flect_test.go
+++ b/flect_test.go
@@ -322,6 +322,28 @@ var singlePluralAssertions = []dict{
 	{"waste", "wastes", true, true},
 	{"psi", "psis", true, true},
 	{"pepsi", "pepsis", true, true},
+
+	// Acronyms
+	{"widget_uuid", "widget_uuids", true, true},
+	{"WidgetUUID", "WidgetUUIDs", true, true},
+	{"widgetUUID", "widgetUUIDs", true, true},
+	{"widgetUuid", "widgetUuids", true, true},
+	{"widget_UUID", "widget_UUIDs", true, true},
+
+	{"ID", "IDs", true, true},
+	{"IDS", "IDSes", true, true},
+	// id to ids (ID), ids to idses (IDS) is not supported
+	{"api", "apis", true, true},
+	{"API", "APIs", true, true},
+	{"html", "htmls", true, true},
+	{"HTML", "HTMLs", true, true},
+	{"FYI", "FYIs", true, true},
+	{"LAN", "LANs", true, true},
+	{"ssh", "sshs", true, true}, // sh
+	{"SSH", "SSHs", true, true},
+	{"eia", "eias", true, true}, // ia
+	{"EIA", "EIAs", true, true},
+	{"DNS", "DNSes", true, true},
 }
 
 func init() {
diff --git a/plural_rules.go b/plural_rules.go
index 53c6081..3904e79 100644
--- a/plural_rules.go
+++ b/plural_rules.go
@@ -202,6 +202,9 @@ var dictionary = []word{
 	{singular: "shoe", plural: "shoes"},
 	{singular: "toe", plural: "toes", exact: true},
 	{singular: "graffiti", plural: "graffiti"},
+
+	// abbreviations
+	{singular: "ID", plural: "IDs", exact: true},
 }
 
 // singleToPlural is the highest priority map for Pluralize().
@@ -366,6 +369,9 @@ var singularToPluralSuffixList = []singularToPluralSuffix{
 	{"o", "oes"},
 	{"x", "xes"},
 
+	// for abbreviations
+	{"S", "Ses"},
+
 	// excluded rules: seems rare
 	// Words from Hebrew that add -im or -ot (eg, cherub becomes cherubim)
 	// - cherub (cherubs or cherubim), seraph (seraphs or seraphim)
diff --git a/pluralize.go b/pluralize.go
index a983f72..d0ac77d 100644
--- a/pluralize.go
+++ b/pluralize.go
@@ -38,6 +38,14 @@ func (i Ident) Pluralize() Ident {
 	pluralMoot.RLock()
 	defer pluralMoot.RUnlock()
 
+	// check if the Original has an explicit entry in the map
+	if p, ok := singleToPlural[i.Original]; ok {
+		return i.ReplaceSuffix(i.Original, p)
+	}
+	if _, ok := pluralToSingle[i.Original]; ok {
+		return i
+	}
+
 	ls := strings.ToLower(s)
 	if _, ok := pluralToSingle[ls]; ok {
 		return i
@@ -51,7 +59,7 @@ func (i Ident) Pluralize() Ident {
 	}
 
 	for _, r := range pluralRules {
-		if strings.HasSuffix(ls, r.suffix) {
+		if strings.HasSuffix(s, r.suffix) {
 			return i.ReplaceSuffix(s, r.fn(s))
 		}
 	}
diff --git a/singularize.go b/singularize.go
index 9993d65..d00cf4f 100644
--- a/singularize.go
+++ b/singularize.go
@@ -35,6 +35,14 @@ func (i Ident) Singularize() Ident {
 	singularMoot.RLock()
 	defer singularMoot.RUnlock()
 
+	// check if the Original has an explicit entry in the map
+	if p, ok := pluralToSingle[i.Original]; ok {
+		return i.ReplaceSuffix(i.Original, p)
+	}
+	if _, ok := singleToPlural[i.Original]; ok {
+		return i
+	}
+
 	ls := strings.ToLower(s)
 	if p, ok := pluralToSingle[ls]; ok {
 		if s == Capitalize(s) {
@@ -48,7 +56,7 @@ func (i Ident) Singularize() Ident {
 	}
 
 	for _, r := range singularRules {
-		if strings.HasSuffix(ls, r.suffix) {
+		if strings.HasSuffix(s, r.suffix) {
 			return i.ReplaceSuffix(s, r.fn(s))
 		}
 	}