diff --git a/deploy/charts/cert-manager/crds/certificates.yaml b/deploy/charts/cert-manager/crds/certificates.yaml
index a57b3d835..b1a5390bc 100644
--- a/deploy/charts/cert-manager/crds/certificates.yaml
+++ b/deploy/charts/cert-manager/crds/certificates.yaml
@@ -96,6 +96,12 @@ spec:
               duration:
                 description: Certificate default Duration
                 type: string
+              emailSANs:
+                description: EmailSANs is a list of Email Subject Alternative Names
+                  to be set on this Certificate.
+                type: array
+                items:
+                  type: string
               ipAddresses:
                 description: IPAddresses is a list of IP addresses to be used on the
                   Certificate
@@ -337,6 +343,12 @@ spec:
               duration:
                 description: Certificate default Duration
                 type: string
+              emailSANs:
+                description: EmailSANs is a list of Email Subject Alternative Names
+                  to be set on this Certificate.
+                type: array
+                items:
+                  type: string
               ipAddresses:
                 description: IPAddresses is a list of IP addresses to be used on the
                   Certificate
diff --git a/deploy/manifests/00-crds.yaml b/deploy/manifests/00-crds.yaml
index 773e225ce..3a015549f 100644
--- a/deploy/manifests/00-crds.yaml
+++ b/deploy/manifests/00-crds.yaml
@@ -302,6 +302,12 @@ spec:
               duration:
                 description: Certificate default Duration
                 type: string
+              emailSANs:
+                description: EmailSANs is a list of Email Subject Alternative Names
+                  to be set on this Certificate.
+                type: array
+                items:
+                  type: string
               ipAddresses:
                 description: IPAddresses is a list of IP addresses to be used on the
                   Certificate
@@ -543,6 +549,12 @@ spec:
               duration:
                 description: Certificate default Duration
                 type: string
+              emailSANs:
+                description: EmailSANs is a list of Email Subject Alternative Names
+                  to be set on this Certificate.
+                type: array
+                items:
+                  type: string
               ipAddresses:
                 description: IPAddresses is a list of IP addresses to be used on the
                   Certificate
diff --git a/pkg/apis/certmanager/v1alpha2/types_certificate.go b/pkg/apis/certmanager/v1alpha2/types_certificate.go
index ceb9914cf..d66dd3d50 100644
--- a/pkg/apis/certmanager/v1alpha2/types_certificate.go
+++ b/pkg/apis/certmanager/v1alpha2/types_certificate.go
@@ -109,6 +109,11 @@ type CertificateSpec struct {
 	// +optional
 	URISANs []string `json:"uriSANs,omitempty"`
 
+	// EmailSANs is a list of Email Subject Alternative Names to be set on this
+	// Certificate.
+	// +optional
+	EmailSANs []string `json:"emailSANs,omitempty"`
+
 	// SecretName is the name of the secret resource to store this secret in
 	SecretName string `json:"secretName"`
 
diff --git a/pkg/apis/certmanager/v1alpha2/zz_generated.deepcopy.go b/pkg/apis/certmanager/v1alpha2/zz_generated.deepcopy.go
index 1ab249c59..952bf2034 100644
--- a/pkg/apis/certmanager/v1alpha2/zz_generated.deepcopy.go
+++ b/pkg/apis/certmanager/v1alpha2/zz_generated.deepcopy.go
@@ -312,6 +312,11 @@ func (in *CertificateSpec) DeepCopyInto(out *CertificateSpec) {
 		*out = make([]string, len(*in))
 		copy(*out, *in)
 	}
+	if in.EmailSANs != nil {
+		in, out := &in.EmailSANs, &out.EmailSANs
+		*out = make([]string, len(*in))
+		copy(*out, *in)
+	}
 	out.IssuerRef = in.IssuerRef
 	if in.Usages != nil {
 		in, out := &in.Usages, &out.Usages
diff --git a/pkg/apis/certmanager/v1alpha3/types_certificate.go b/pkg/apis/certmanager/v1alpha3/types_certificate.go
index ed371da1f..c9dcc8064 100644
--- a/pkg/apis/certmanager/v1alpha3/types_certificate.go
+++ b/pkg/apis/certmanager/v1alpha3/types_certificate.go
@@ -105,6 +105,11 @@ type CertificateSpec struct {
 	// +optional
 	URISANs []string `json:"uriSANs,omitempty"`
 
+	// EmailSANs is a list of Email Subject Alternative Names to be set on this
+	// Certificate.
+	// +optional
+	EmailSANs []string `json:"emailSANs,omitempty"`
+
 	// SecretName is the name of the secret resource to store this secret in
 	SecretName string `json:"secretName"`
 
diff --git a/pkg/apis/certmanager/v1alpha3/zz_generated.deepcopy.go b/pkg/apis/certmanager/v1alpha3/zz_generated.deepcopy.go
index fb5b6ae23..dbabbf9ae 100644
--- a/pkg/apis/certmanager/v1alpha3/zz_generated.deepcopy.go
+++ b/pkg/apis/certmanager/v1alpha3/zz_generated.deepcopy.go
@@ -307,6 +307,11 @@ func (in *CertificateSpec) DeepCopyInto(out *CertificateSpec) {
 		*out = make([]string, len(*in))
 		copy(*out, *in)
 	}
+	if in.EmailSANs != nil {
+		in, out := &in.EmailSANs, &out.EmailSANs
+		*out = make([]string, len(*in))
+		copy(*out, *in)
+	}
 	out.IssuerRef = in.IssuerRef
 	if in.Usages != nil {
 		in, out := &in.Usages, &out.Usages
diff --git a/pkg/controller/webhookbootstrap/controller.go b/pkg/controller/webhookbootstrap/controller.go
index 0be79c82c..0c213a341 100644
--- a/pkg/controller/webhookbootstrap/controller.go
+++ b/pkg/controller/webhookbootstrap/controller.go
@@ -333,6 +333,12 @@ func (c *controller) certificateRequiresIssuance(ctx context.Context, log logr.L
 		return true
 	}
 
+	// validate the email addressed are correct
+	if !util.EqualUnsorted(cert.EmailAddresses, crt.Spec.EmailSANs) {
+		log.Info("certificate email addresses are not as expected, re-issuing")
+		return true
+	}
+
 	if c.certificateNeedsRenew(ctx, cert, crt) {
 		log.Info("certificate requires renewal, re-issuing")
 		return true
diff --git a/pkg/internal/apis/certmanager/types_certificate.go b/pkg/internal/apis/certmanager/types_certificate.go
index 015347106..bb53684d3 100644
--- a/pkg/internal/apis/certmanager/types_certificate.go
+++ b/pkg/internal/apis/certmanager/types_certificate.go
@@ -86,6 +86,10 @@ type CertificateSpec struct {
 	// Certificate.
 	URISANs []string
 
+	// EmailSANs is a list of Email Subject Alternative Names to be set on this
+	// Certificate.
+	EmailSANs []string
+
 	// SecretName is the name of the secret resource to store this secret in
 	SecretName string
 
diff --git a/pkg/internal/apis/certmanager/v1alpha2/zz_generated.conversion.go b/pkg/internal/apis/certmanager/v1alpha2/zz_generated.conversion.go
index 51e8bdbd8..84c80d897 100644
--- a/pkg/internal/apis/certmanager/v1alpha2/zz_generated.conversion.go
+++ b/pkg/internal/apis/certmanager/v1alpha2/zz_generated.conversion.go
@@ -605,6 +605,7 @@ func autoConvert_v1alpha2_CertificateSpec_To_certmanager_CertificateSpec(in *v1a
 	out.DNSNames = *(*[]string)(unsafe.Pointer(&in.DNSNames))
 	out.IPAddresses = *(*[]string)(unsafe.Pointer(&in.IPAddresses))
 	out.URISANs = *(*[]string)(unsafe.Pointer(&in.URISANs))
+	out.EmailSANs = *(*[]string)(unsafe.Pointer(&in.EmailSANs))
 	out.SecretName = in.SecretName
 	// TODO: Inefficient conversion - can we improve it?
 	if err := s.Convert(&in.IssuerRef, &out.IssuerRef, 0); err != nil {
@@ -634,6 +635,7 @@ func autoConvert_certmanager_CertificateSpec_To_v1alpha2_CertificateSpec(in *cer
 	out.DNSNames = *(*[]string)(unsafe.Pointer(&in.DNSNames))
 	out.IPAddresses = *(*[]string)(unsafe.Pointer(&in.IPAddresses))
 	out.URISANs = *(*[]string)(unsafe.Pointer(&in.URISANs))
+	out.EmailSANs = *(*[]string)(unsafe.Pointer(&in.EmailSANs))
 	out.SecretName = in.SecretName
 	// TODO: Inefficient conversion - can we improve it?
 	if err := s.Convert(&in.IssuerRef, &out.IssuerRef, 0); err != nil {
diff --git a/pkg/internal/apis/certmanager/v1alpha3/zz_generated.conversion.go b/pkg/internal/apis/certmanager/v1alpha3/zz_generated.conversion.go
index eb83852ef..c63078cd2 100644
--- a/pkg/internal/apis/certmanager/v1alpha3/zz_generated.conversion.go
+++ b/pkg/internal/apis/certmanager/v1alpha3/zz_generated.conversion.go
@@ -576,6 +576,7 @@ func autoConvert_v1alpha3_CertificateSpec_To_certmanager_CertificateSpec(in *v1a
 	out.DNSNames = *(*[]string)(unsafe.Pointer(&in.DNSNames))
 	out.IPAddresses = *(*[]string)(unsafe.Pointer(&in.IPAddresses))
 	out.URISANs = *(*[]string)(unsafe.Pointer(&in.URISANs))
+	out.EmailSANs = *(*[]string)(unsafe.Pointer(&in.EmailSANs))
 	out.SecretName = in.SecretName
 	// TODO: Inefficient conversion - can we improve it?
 	if err := s.Convert(&in.IssuerRef, &out.IssuerRef, 0); err != nil {
@@ -602,6 +603,7 @@ func autoConvert_certmanager_CertificateSpec_To_v1alpha3_CertificateSpec(in *cer
 	out.DNSNames = *(*[]string)(unsafe.Pointer(&in.DNSNames))
 	out.IPAddresses = *(*[]string)(unsafe.Pointer(&in.IPAddresses))
 	out.URISANs = *(*[]string)(unsafe.Pointer(&in.URISANs))
+	out.EmailSANs = *(*[]string)(unsafe.Pointer(&in.EmailSANs))
 	out.SecretName = in.SecretName
 	// TODO: Inefficient conversion - can we improve it?
 	if err := s.Convert(&in.IssuerRef, &out.IssuerRef, 0); err != nil {
diff --git a/pkg/internal/apis/certmanager/validation/certificate.go b/pkg/internal/apis/certmanager/validation/certificate.go
index dbd1c4af6..a5705852b 100644
--- a/pkg/internal/apis/certmanager/validation/certificate.go
+++ b/pkg/internal/apis/certmanager/validation/certificate.go
@@ -19,6 +19,7 @@ package validation
 import (
 	"fmt"
 	"net"
+	"net/mail"
 
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/util/validation/field"
@@ -39,9 +40,8 @@ func ValidateCertificateSpec(crt *cmapi.CertificateSpec, fldPath *field.Path) fi
 
 	el = append(el, validateIssuerRef(crt.IssuerRef, fldPath)...)
 
-	if len(crt.CommonName) == 0 && len(crt.DNSNames) == 0 && len(crt.URISANs) == 0 {
-		el = append(el, field.Required(fldPath.Child("commonName", "dnsNames", "uriSANs"),
-			"at least one of commonName, dnsNames, or uriSANs must be set"))
+	if len(crt.CommonName) == 0 && len(crt.DNSNames) == 0 && len(crt.URISANs) == 0 && len(crt.EmailSANs) == 0 {
+		el = append(el, field.Invalid(fldPath, "", "at least one of commonName, dnsNames, uriSANs or emailSANs must be set"))
 	}
 
 	// if a common name has been specified, ensure it is no longer than 64 chars
@@ -52,6 +52,11 @@ func ValidateCertificateSpec(crt *cmapi.CertificateSpec, fldPath *field.Path) fi
 	if len(crt.IPAddresses) > 0 {
 		el = append(el, validateIPAddresses(crt, fldPath)...)
 	}
+
+	if len(crt.EmailSANs) > 0 {
+		el = append(el, validateEmailAddresses(crt, fldPath)...)
+	}
+
 	switch crt.KeyAlgorithm {
 	case cmapi.KeyAlgorithm(""):
 	case cmapi.RSAKeyAlgorithm:
@@ -113,6 +118,24 @@ func validateIPAddresses(a *cmapi.CertificateSpec, fldPath *field.Path) field.Er
 	return el
 }
 
+func validateEmailAddresses(a *cmapi.CertificateSpec, fldPath *field.Path) field.ErrorList {
+	if len(a.EmailSANs) <= 0 {
+		return nil
+	}
+	el := field.ErrorList{}
+	for i, d := range a.EmailSANs {
+		e, err := mail.ParseAddress(d)
+		if err != nil {
+			el = append(el, field.Invalid(fldPath.Child("emailSANs").Index(i), d, fmt.Sprintf("invalid email address: %s", err)))
+		} else if e.Address != d {
+			// Go accepts email names as per RFC 5322 (name <email>)
+			// This checks if the supplied value only contains the email address and nothing else
+			el = append(el, field.Invalid(fldPath.Child("emailSANs").Index(i), d, "invalid email address: make sure the supplied value only contains the email address itself"))
+		}
+	}
+	return el
+}
+
 func validateUsages(a *cmapi.CertificateSpec, fldPath *field.Path) field.ErrorList {
 	el := field.ErrorList{}
 	for i, u := range a.Usages {
diff --git a/pkg/internal/apis/certmanager/validation/certificate_test.go b/pkg/internal/apis/certmanager/validation/certificate_test.go
index 0beb75cb3..6ca6e38c1 100644
--- a/pkg/internal/apis/certmanager/validation/certificate_test.go
+++ b/pkg/internal/apis/certmanager/validation/certificate_test.go
@@ -125,7 +125,7 @@ func TestValidateCertificate(t *testing.T) {
 				},
 			},
 			errs: []*field.Error{
-				field.Required(fldPath.Child("commonName", "dnsNames", "uriSANs"), "at least one of commonName, dnsNames, or uriSANs must be set"),
+				field.Invalid(fldPath, "", "at least one of commonName, dnsNames, uriSANs or emailSANs must be set"),
 			},
 		},
 		"certificate with no issuerRef": {
@@ -413,6 +413,51 @@ func TestValidateCertificate(t *testing.T) {
 				},
 			},
 		},
+		"valid certificate with only email SAN": {
+			cfg: &cmapi.Certificate{
+				Spec: cmapi.CertificateSpec{
+					EmailSANs:  []string{"alice@example.com"},
+					SecretName: "abc",
+					IssuerRef:  validIssuerRef,
+				},
+			},
+		},
+		"invalid certificate with incorrect email": {
+			cfg: &cmapi.Certificate{
+				Spec: cmapi.CertificateSpec{
+					EmailSANs:  []string{"aliceexample.com"},
+					SecretName: "abc",
+					IssuerRef:  validIssuerRef,
+				},
+			},
+			errs: []*field.Error{
+				field.Invalid(fldPath.Child("emailSANs").Index(0), "aliceexample.com", "invalid email address: mail: missing '@' or angle-addr"),
+			},
+		},
+		"invalid certificate with email formatted with name": {
+			cfg: &cmapi.Certificate{
+				Spec: cmapi.CertificateSpec{
+					EmailSANs:  []string{"Alice <alice@example.com>"},
+					SecretName: "abc",
+					IssuerRef:  validIssuerRef,
+				},
+			},
+			errs: []*field.Error{
+				field.Invalid(fldPath.Child("emailSANs").Index(0), "Alice <alice@example.com>", "invalid email address: make sure the supplied value only contains the email address itself"),
+			},
+		},
+		"invalid certificate with email formatted with mailto": {
+			cfg: &cmapi.Certificate{
+				Spec: cmapi.CertificateSpec{
+					EmailSANs:  []string{"mailto:alice@example.com"},
+					SecretName: "abc",
+					IssuerRef:  validIssuerRef,
+				},
+			},
+			errs: []*field.Error{
+				field.Invalid(fldPath.Child("emailSANs").Index(0), "mailto:alice@example.com", "invalid email address: mail: expected comma"),
+			},
+		},
 	}
 	for n, s := range scenarios {
 		t.Run(n, func(t *testing.T) {
diff --git a/pkg/internal/apis/certmanager/zz_generated.deepcopy.go b/pkg/internal/apis/certmanager/zz_generated.deepcopy.go
index c61b8c754..f96bbcffa 100644
--- a/pkg/internal/apis/certmanager/zz_generated.deepcopy.go
+++ b/pkg/internal/apis/certmanager/zz_generated.deepcopy.go
@@ -307,6 +307,11 @@ func (in *CertificateSpec) DeepCopyInto(out *CertificateSpec) {
 		*out = make([]string, len(*in))
 		copy(*out, *in)
 	}
+	if in.EmailSANs != nil {
+		in, out := &in.EmailSANs, &out.EmailSANs
+		*out = make([]string, len(*in))
+		copy(*out, *in)
+	}
 	out.IssuerRef = in.IssuerRef
 	if in.Usages != nil {
 		in, out := &in.Usages, &out.Usages
diff --git a/pkg/util/pki/csr.go b/pkg/util/pki/csr.go
index 7767d42fc..12c394050 100644
--- a/pkg/util/pki/csr.go
+++ b/pkg/util/pki/csr.go
@@ -188,8 +188,8 @@ func GenerateCSR(crt *v1alpha2.Certificate) (*x509.CertificateRequest, error) {
 		return nil, err
 	}
 
-	if len(commonName) == 0 && len(dnsNames) == 0 && len(uriNames) == 0 {
-		return nil, fmt.Errorf("no common name, DNS name, or URI SAN specified on certificate")
+	if len(commonName) == 0 && len(dnsNames) == 0 && len(uriNames) == 0 && len(crt.Spec.EmailSANs) == 0 {
+		return nil, fmt.Errorf("no common name, DNS name, URI SAN, or Email SAN specified on certificate")
 	}
 
 	pubKeyAlgo, sigAlgo, err := SignatureAlgorithm(crt)
@@ -212,9 +212,10 @@ func GenerateCSR(crt *v1alpha2.Certificate) (*x509.CertificateRequest, error) {
 			SerialNumber:       subject.SerialNumber,
 			CommonName:         commonName,
 		},
-		DNSNames:    dnsNames,
-		IPAddresses: iPAddresses,
-		URIs:        uriNames,
+		DNSNames:       dnsNames,
+		IPAddresses:    iPAddresses,
+		URIs:           uriNames,
+		EmailAddresses: crt.Spec.EmailSANs,
 		// TODO: work out how best to handle extensions/key usages here
 		ExtraExtensions: []pkix.Extension{},
 	}, nil
@@ -271,10 +272,11 @@ func GenerateTemplate(crt *v1alpha2.Certificate) (*x509.Certificate, error) {
 		NotBefore: time.Now(),
 		NotAfter:  time.Now().Add(certDuration),
 		// see http://golang.org/pkg/crypto/x509/#KeyUsage
-		KeyUsage:    keyUsages,
-		ExtKeyUsage: extKeyUsages,
-		DNSNames:    dnsNames,
-		IPAddresses: ipAddresses,
+		KeyUsage:       keyUsages,
+		ExtKeyUsage:    extKeyUsages,
+		DNSNames:       dnsNames,
+		IPAddresses:    ipAddresses,
+		EmailAddresses: crt.Spec.EmailSANs,
 	}, nil
 }
 
@@ -328,11 +330,12 @@ func GenerateTemplateFromCSRPEMWithUsages(csrPEM []byte, duration time.Duration,
 		NotBefore:             time.Now(),
 		NotAfter:              time.Now().Add(duration),
 		// see http://golang.org/pkg/crypto/x509/#KeyUsage
-		KeyUsage:    keyUsage,
-		ExtKeyUsage: extKeyUsage,
-		DNSNames:    csr.DNSNames,
-		IPAddresses: csr.IPAddresses,
-		URIs:        csr.URIs,
+		KeyUsage:       keyUsage,
+		ExtKeyUsage:    extKeyUsage,
+		DNSNames:       csr.DNSNames,
+		IPAddresses:    csr.IPAddresses,
+		EmailAddresses: csr.EmailAddresses,
+		URIs:           csr.URIs,
 	}, nil
 }
 
diff --git a/test/e2e/framework/helper/certificates.go b/test/e2e/framework/helper/certificates.go
index de4131792..11c43132f 100644
--- a/test/e2e/framework/helper/certificates.go
+++ b/test/e2e/framework/helper/certificates.go
@@ -213,6 +213,10 @@ func (h *Helper) ValidateIssuedCertificate(certificate *cmapi.Certificate, rootC
 			apiutil.ExtKeyUsageStrings(certificateExtKeyUsages), apiutil.ExtKeyUsageStrings(cert.ExtKeyUsage))
 	}
 
+	if !util.EqualUnsorted(cert.EmailAddresses, certificate.Spec.EmailSANs) {
+		return nil, fmt.Errorf("certificate doesn't contain Email SANs: exp=%v got=%v", certificate.Spec.EmailSANs, cert.EmailAddresses)
+	}
+
 	var dnsName string
 	if len(expectedDNSNames) > 0 {
 		dnsName = expectedDNSNames[0]
diff --git a/test/e2e/suite/conformance/certificates/acme/acme.go b/test/e2e/suite/conformance/certificates/acme/acme.go
index f367f0858..49a67647e 100644
--- a/test/e2e/suite/conformance/certificates/acme/acme.go
+++ b/test/e2e/suite/conformance/certificates/acme/acme.go
@@ -54,6 +54,7 @@ func runACMEIssuerTests(eab *cmacme.ACMEExternalAccountBinding) {
 		certificates.URISANsFeature,
 		certificates.CommonNameFeature,
 		certificates.KeyUsagesFeature,
+		certificates.EmailSANsFeature,
 	)
 
 	// unsupportedDNS01Features is a list of features that are not supported by the ACME
@@ -64,6 +65,7 @@ func runACMEIssuerTests(eab *cmacme.ACMEExternalAccountBinding) {
 		certificates.URISANsFeature,
 		certificates.CommonNameFeature,
 		certificates.KeyUsagesFeature,
+		certificates.EmailSANsFeature,
 	)
 
 	provisionerHTTP01 := &acmeIssuerProvisioner{
diff --git a/test/e2e/suite/conformance/certificates/featureset.go b/test/e2e/suite/conformance/certificates/featureset.go
index 238f6e56b..5ec1e27d9 100644
--- a/test/e2e/suite/conformance/certificates/featureset.go
+++ b/test/e2e/suite/conformance/certificates/featureset.go
@@ -103,6 +103,10 @@ const (
 	// that includes a URISANs. ACME providers do not support this.
 	URISANsFeature Feature = "URISANs"
 
+	// EmailSANs denotes whether to the target issuer is able to sign a certificate
+	// that includes a EmailSANs.
+	EmailSANsFeature Feature = "EmailSANs"
+
 	// CommonName denotes whether the target issuer is able to sign certificates
 	// with a distinct CommonName. This is useful for issuers such as ACME
 	// providers that ignore, or otherwise have special requirements for the
diff --git a/test/e2e/suite/conformance/certificates/suite.go b/test/e2e/suite/conformance/certificates/suite.go
index 258ded81f..59dbd2d4f 100644
--- a/test/e2e/suite/conformance/certificates/suite.go
+++ b/test/e2e/suite/conformance/certificates/suite.go
@@ -242,6 +242,30 @@ func (s *Suite) Define() {
 			Expect(err).NotTo(HaveOccurred())
 		})
 
+		It("should issue a certificate that defines an Email Address", func() {
+			s.checkFeatures(EmailSANsFeature)
+
+			testCertificate := &cmapi.Certificate{
+				ObjectMeta: metav1.ObjectMeta{
+					Name:      "testcert",
+					Namespace: f.Namespace.Name,
+				},
+				Spec: cmapi.CertificateSpec{
+					SecretName: "testcert-tls",
+					EmailSANs:  []string{"alice@example.com"},
+					IssuerRef:  issuerRef,
+				},
+			}
+			By("Creating a Certificate")
+			err := f.CRClient.Create(ctx, testCertificate)
+			Expect(err).NotTo(HaveOccurred())
+
+			By("Waiting for the Certificate to be issued...")
+			err = f.Helper().WaitCertificateIssuedValid(f.Namespace.Name, "testcert", time.Minute*5)
+			Expect(err).NotTo(HaveOccurred())
+
+		})
+
 		It("should issue a certificate that defines a CommonName and URI SAN", func() {
 			s.checkFeatures(URISANsFeature)
 			s.checkFeatures(CommonNameFeature)