diff --git a/crates/domain/src/authority.rs b/crates/domain/src/authority.rs
new file mode 100644
index 0000000..299b1a1
--- /dev/null
+++ b/crates/domain/src/authority.rs
@@ -0,0 +1,86 @@
+use serde::{Deserialize, Serialize};
+
+use crate::{AuthorityId, LocalizedLabel};
+
+/// The kind of authority record.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum AuthorityKind {
+    Person,
+    Organisation,
+    Place,
+}
+
+impl AuthorityKind {
+    pub fn as_str(&self) -> &'static str {
+        match self {
+            AuthorityKind::Person => "person",
+            AuthorityKind::Organisation => "organisation",
+            AuthorityKind::Place => "place",
+        }
+    }
+
+    pub fn from_db(s: &str) -> Option<Self> {
+        match s {
+            "person" => Some(AuthorityKind::Person),
+            "organisation" => Some(AuthorityKind::Organisation),
+            "place" => Some(AuthorityKind::Place),
+            _ => None,
+        }
+    }
+}
+
+/// An authority record (person / organisation / place), with multilingual labels.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Authority {
+    pub id: AuthorityId,
+    pub kind: AuthorityKind,
+    pub external_uri: Option<String>,
+    pub labels: Vec<LocalizedLabel>,
+}
+
+/// An authority to be created.
+#[derive(Debug, Clone, PartialEq)]
+pub struct NewAuthority {
+    pub kind: AuthorityKind,
+    pub external_uri: Option<String>,
+    pub labels: Vec<LocalizedLabel>,
+}
+
+/// A reference to an authority confirmed to exist (carries its kind).
+///
+/// Obtain via `db::authority::resolve_authority`.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub struct AuthorityRef {
+    authority_id: AuthorityId,
+    kind: AuthorityKind,
+}
+
+impl AuthorityRef {
+    pub fn new(authority_id: AuthorityId, kind: AuthorityKind) -> Self {
+        Self { authority_id, kind }
+    }
+    pub fn authority_id(&self) -> AuthorityId {
+        self.authority_id
+    }
+    pub fn kind(&self) -> AuthorityKind {
+        self.kind
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn kind_round_trips_via_db_string() {
+        for k in [
+            AuthorityKind::Person,
+            AuthorityKind::Organisation,
+            AuthorityKind::Place,
+        ] {
+            assert_eq!(AuthorityKind::from_db(k.as_str()), Some(k));
+        }
+        assert_eq!(AuthorityKind::from_db("ufo"), None);
+    }
+}
diff --git a/crates/domain/src/id.rs b/crates/domain/src/id.rs
index 648e315..7990fb2 100644
--- a/crates/domain/src/id.rs
+++ b/crates/domain/src/id.rs
@@ -1,53 +1,69 @@
-use std::fmt;
-use std::str::FromStr;
+//! Strongly-typed identifiers.
 
-use serde::{Deserialize, Serialize};
-use uuid::Uuid;
+/// Define a UUID newtype identifier with the standard constructors and conversions.
+macro_rules! id_newtype {
+    ($(#[$meta:meta])* $name:ident) => {
+        $(#[$meta])*
+        #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, serde::Serialize, serde::Deserialize)]
+        #[serde(transparent)]
+        pub struct $name(uuid::Uuid);
 
-/// Identifier for an organization (tenant).
-///
-/// A newtype over [`Uuid`] so it can never be confused with another entity's id.
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Serialize, Deserialize)]
-#[serde(transparent)]
-pub struct OrgId(Uuid);
+        impl $name {
+            /// Generate a fresh random id.
+            #[must_use]
+            pub fn new() -> Self {
+                Self(uuid::Uuid::new_v4())
+            }
 
-impl OrgId {
-    /// Generate a fresh random id.
-    #[must_use = "generating an OrgId and discarding it is almost certainly a mistake"]
-    pub fn new() -> Self {
-        Self(Uuid::new_v4())
-    }
+            /// Wrap an existing [`uuid::Uuid`].
+            pub fn from_uuid(uuid: uuid::Uuid) -> Self {
+                Self(uuid)
+            }
 
-    /// Wrap an existing [`Uuid`].
-    pub fn from_uuid(uuid: Uuid) -> Self {
-        Self(uuid)
-    }
+            /// The underlying [`uuid::Uuid`].
+            pub fn to_uuid(&self) -> uuid::Uuid {
+                self.0
+            }
+        }
 
-    /// Return the underlying [`Uuid`].
-    pub fn to_uuid(&self) -> Uuid {
-        self.0
-    }
+        impl Default for $name {
+            fn default() -> Self {
+                Self::new()
+            }
+        }
+
+        impl std::fmt::Display for $name {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                std::fmt::Display::fmt(&self.0, f)
+            }
+        }
+
+        impl std::str::FromStr for $name {
+            type Err = uuid::Error;
+
+            fn from_str(s: &str) -> Result<Self, Self::Err> {
+                Ok(Self(uuid::Uuid::parse_str(s)?))
+            }
+        }
+    };
 }
 
-impl Default for OrgId {
-    fn default() -> Self {
-        Self::new()
-    }
-}
-
-impl fmt::Display for OrgId {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Display::fmt(&self.0, f)
-    }
-}
-
-impl FromStr for OrgId {
-    type Err = uuid::Error;
-
-    fn from_str(s: &str) -> Result<Self, Self::Err> {
-        Ok(Self(Uuid::parse_str(s)?))
-    }
-}
+id_newtype!(
+    /// Identifier for an organization (tenant).
+    OrgId
+);
+id_newtype!(
+    /// Identifier for a controlled vocabulary (term source).
+    VocabularyId
+);
+id_newtype!(
+    /// Identifier for a term within a vocabulary.
+    TermId
+);
+id_newtype!(
+    /// Identifier for an authority record (person, organisation, or place).
+    AuthorityId
+);
 
 #[cfg(test)]
 mod tests {
@@ -64,4 +80,12 @@ mod tests {
     fn rejects_invalid_uuid() {
         assert!("not-a-uuid".parse::<OrgId>().is_err());
     }
+
+    #[test]
+    fn distinct_id_types_parse_independently() {
+        let text = "550e8400-e29b-41d4-a716-446655440000";
+        assert_eq!(text.parse::<VocabularyId>().unwrap().to_string(), text);
+        assert_eq!(text.parse::<TermId>().unwrap().to_string(), text);
+        assert_eq!(text.parse::<AuthorityId>().unwrap().to_string(), text);
+    }
 }
diff --git a/crates/domain/src/label.rs b/crates/domain/src/label.rs
new file mode 100644
index 0000000..45fd981
--- /dev/null
+++ b/crates/domain/src/label.rs
@@ -0,0 +1,48 @@
+use serde::{Deserialize, Serialize};
+
+/// A label in a specific language (BCP-47 tag, e.g. "sv", "en").
+#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
+pub struct LocalizedLabel {
+    pub lang: String,
+    pub label: String,
+}
+
+/// Pick the best label for `lang`, falling back to `fallback`, then the first.
+pub fn pick_label<'a>(labels: &'a [LocalizedLabel], lang: &str, fallback: &str) -> Option<&'a str> {
+    labels
+        .iter()
+        .find(|l| l.lang == lang)
+        .or_else(|| labels.iter().find(|l| l.lang == fallback))
+        .or_else(|| labels.first())
+        .map(|l| l.label.as_str())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn sample() -> Vec<LocalizedLabel> {
+        vec![
+            LocalizedLabel {
+                lang: "sv".into(),
+                label: "trä".into(),
+            },
+            LocalizedLabel {
+                lang: "en".into(),
+                label: "wood".into(),
+            },
+        ]
+    }
+
+    #[test]
+    fn prefers_requested_language() {
+        assert_eq!(pick_label(&sample(), "sv", "en"), Some("trä"));
+    }
+
+    #[test]
+    fn falls_back_then_first() {
+        assert_eq!(pick_label(&sample(), "de", "en"), Some("wood"));
+        assert_eq!(pick_label(&sample(), "de", "fr"), Some("trä"));
+        assert_eq!(pick_label(&[], "sv", "en"), None);
+    }
+}
diff --git a/crates/domain/src/lib.rs b/crates/domain/src/lib.rs
index 8a20e46..d5809c4 100644
--- a/crates/domain/src/lib.rs
+++ b/crates/domain/src/lib.rs
@@ -1,7 +1,13 @@
 //! Core domain types and invariants. No I/O dependencies.
 
 mod audit;
+mod authority;
 mod id;
+mod label;
+mod vocabulary;
 
 pub use audit::{AuditAction, AuditActor, AuditEntry, FieldChange, NewAuditEvent};
-pub use id::OrgId;
+pub use authority::{Authority, AuthorityKind, AuthorityRef, NewAuthority};
+pub use id::{AuthorityId, OrgId, TermId, VocabularyId};
+pub use label::{LocalizedLabel, pick_label};
+pub use vocabulary::{NewTerm, Term, TermRef, Vocabulary};
diff --git a/crates/domain/src/vocabulary.rs b/crates/domain/src/vocabulary.rs
new file mode 100644
index 0000000..2be29b7
--- /dev/null
+++ b/crates/domain/src/vocabulary.rs
@@ -0,0 +1,52 @@
+use serde::{Deserialize, Serialize};
+
+use crate::{LocalizedLabel, TermId, VocabularyId};
+
+/// A controlled vocabulary (term source), e.g. "material" or "object_name".
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Vocabulary {
+    pub id: VocabularyId,
+    pub key: String,
+}
+
+/// A term within a vocabulary, with its multilingual labels.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Term {
+    pub id: TermId,
+    pub vocabulary_id: VocabularyId,
+    pub external_uri: Option<String>,
+    pub labels: Vec<LocalizedLabel>,
+}
+
+/// A term to be created.
+#[derive(Debug, Clone, PartialEq)]
+pub struct NewTerm {
+    pub vocabulary_id: VocabularyId,
+    pub external_uri: Option<String>,
+    pub labels: Vec<LocalizedLabel>,
+}
+
+/// A reference to a term confirmed to exist in a given vocabulary.
+///
+/// Obtain via `db::vocab::resolve_term`; do not construct ad hoc for
+/// values that haven't been resolved.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub struct TermRef {
+    term_id: TermId,
+    vocabulary_id: VocabularyId,
+}
+
+impl TermRef {
+    pub fn new(term_id: TermId, vocabulary_id: VocabularyId) -> Self {
+        Self {
+            term_id,
+            vocabulary_id,
+        }
+    }
+    pub fn term_id(&self) -> TermId {
+        self.term_id
+    }
+    pub fn vocabulary_id(&self) -> VocabularyId {
+        self.vocabulary_id
+    }
+}