diff --git a/glossy/README.md b/glossy/README.md
index 5a04649..a9bdc91 100644
--- a/glossy/README.md
+++ b/glossy/README.md
@@ -168,6 +168,19 @@ Display the glossary using the `glossary()` function:
 )
 ```
 
+Note that if you want to display terms without a group, you specify that with an
+empty string. For example, to show the empty group and then the _Web_ group:
+
+```typst
+#glossary(groups: ("", "Web"))
+```
+
+Or to just show the empty group (i.e. terms without a group):
+
+```typst
+#glossary(groups: (""))
+```
+
 ### Customizing Term Display
 
 Control how terms appear in the document by providing a custom `show-term` function:
diff --git a/glossy/src/gloss.typ b/glossy/src/gloss.typ
index 3956ff3..2c2e2e7 100644
--- a/glossy/src/gloss.typ
+++ b/glossy/src/gloss.typ
@@ -1,3 +1,7 @@
+// TODO: replace with @preview when back online
+#import "@preview/valkyrie:0.2.1" as z
+
+#import "./schemas.typ": *
 #import "./themes.typ": *
 #import "./utils.typ": *
 
@@ -332,10 +336,15 @@
   show-term: (term-body) => term-body,
   body
 ) = context {
-  // Validate entries parameter type
-  if type(entries) != dictionary {
-    panic("entries must be a dictionary, instead got: " + repr(entries))
+  // Type checking
+  let checked-entries = (:)
+  for (key, entry) in entries {
+    let checked-key = z.parse(key, z.string(), scope: ("dictionary key",))
+    let checked-entry = z.parse(entry, dict-schema, scope: ("dictionary entry",))
+    checked-entries.insert(checked-key, checked-entry)
   }
+  let checked-show-term = z.parse(show-term, z.function(), scope: ("show-term",))
+  let checked-body = z.parse(body, z.content(), scope: ("body",))
 
   // Process and store each glossary entry
   for (key, entry) in entries {
@@ -396,6 +405,12 @@
   ignore-case: false,
   groups: (),
 ) = context {
+  // Type checking
+  let checked-title = z.parse(title, z.content(), scope: ("title",))
+  let checked-groups = z.parse(groups, groups-list-schema, scope: ("groups",))
+  let checked-ignore-case = z.parse(ignore-case, z.boolean(), scope: ("ignore-case",))
+  let checked-theme = z.parse(theme, theme-schema, scope: ("theme",))
+
   // Collect and organize entries by group
   let output = (:)
   let all_entries = __gloss_entries.final()
@@ -405,19 +420,23 @@
   let all_groups = all_entries
     .values()
     .map(e => e.at("group"))
+    .map(g => { if g == none { "" } else { g } })
     .dedup()
     .sorted()
 
-  let target_groups = if groups.len() == 0 {
+  let target_groups = if checked-groups.len() == 0 {
     all_groups
   } else {
     // Validate requested groups exist
-    for g in groups {
+    for g in checked-groups {
+      if g == none {
+        g = ""
+      }
       if g not in all_groups {
-        panic("Requested group not found: " + g)
+        panic("Requested group, '" + g + "', not found.")
       }
     }
-    groups
+    checked-groups
   }
 
   // Process entries group by group
@@ -459,15 +478,15 @@
   // Render the glossary using the theme
   let group_index = 0
 
-  (theme.section)(
+  (checked-theme.section)(
     title,
     for (group, entries) in output {
-      (theme.group)(
+      (checked-theme.group)(
         group,
         group_index,
         output.len(),
         for (i, entry) in entries.enumerate() {
-          (theme.entry)(entry, i, entries.len())
+          (checked-theme.entry)(entry, i, entries.len())
         }
       )
       group_index += 1
diff --git a/glossy/src/schemas.typ b/glossy/src/schemas.typ
new file mode 100644
index 0000000..949de09
--- /dev/null
+++ b/glossy/src/schemas.typ
@@ -0,0 +1,26 @@
+// TODO: change to @preview when online
+#import "@preview/valkyrie:0.2.1" as z
+
+#let dict-schema = z.either(
+  z.string(),
+  z.dictionary(
+    (
+      short: z.content(), // this is the only required field
+      plural: z.content(optional: true),
+      long: z.content(optional: true),
+      longplural: z.content(optional: true),
+      description: z.content(optional: true),
+      group: z.content(optional: true),
+    )
+  )
+)
+
+#let theme-schema = z.dictionary(
+  (
+    section: z.function(),
+    group: z.function(),
+    entry: z.function(),
+  )
+)
+
+#let groups-list-schema = z.array(pre-transform: z.coerce.array)
diff --git a/glossy/tests/group-specified/abbreviations.json b/glossy/tests/group-specified/abbreviations.json
new file mode 100644
index 0000000..ff4594f
--- /dev/null
+++ b/glossy/tests/group-specified/abbreviations.json
@@ -0,0 +1,11 @@
+{
+  "zbuffer": {
+    "short": "z-bufer",
+    "long": "the depth buffer"
+  },
+  "pbr": {
+    "short": "PBR",
+    "long": "physically based rendering",
+    "group": "abbreviations"
+  }
+}
diff --git a/glossy/tests/group-specified/ref/1.png b/glossy/tests/group-specified/ref/1.png
new file mode 100644
index 0000000..7db97d3
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diff --git a/glossy/tests/group-specified/ref/2.png b/glossy/tests/group-specified/ref/2.png
new file mode 100644
index 0000000..22f8771
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diff --git a/glossy/tests/group-specified/ref/3.png b/glossy/tests/group-specified/ref/3.png
new file mode 100644
index 0000000..e2ba743
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diff --git a/glossy/tests/group-specified/ref/4.png b/glossy/tests/group-specified/ref/4.png
new file mode 100644
index 0000000..d903658
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diff --git a/glossy/tests/group-specified/test.typ b/glossy/tests/group-specified/test.typ
new file mode 100644
index 0000000..58720ae
--- /dev/null
+++ b/glossy/tests/group-specified/test.typ
@@ -0,0 +1,33 @@
+#import "/lib.typ": *
+
+#show: init-glossary.with(json("abbreviations.json"))
+
+Reference: @pbr, @zbuffer
+
+
+#let t(g) = [
+  #line(length: 100%)
+  *TESTING:* `#glossary(groups: ` #repr(g) `)`
+  #glossary(groups: g)
+]
+
+#t("abbreviations")                   // "string" : str
+#t(("abbreviations"))                 // ("string") : str
+#t(("abbreviations",))                // ("string",) : array(str)
+#t(("abbreviations","abbreviations")) // ("string","string",) : array(str)
+
+#pagebreak(weak: true)
+
+#t("")                                // empty string should be the empty group
+#t((""))                              // empty string should be the empty group
+#t(("",))                             // empty string should be the empty group
+#t(("",""))                           // empty string should be the empty group
+
+#pagebreak(weak: true)
+
+#t(none)                              // none should be all groups
+#t((none))                            // none should be all groups
+
+#pagebreak(weak: true)
+
+#t(("abbreviations",none))            // try to get both groups