diff --git a/.changeset/thin-houses-provide.md b/.changeset/thin-houses-provide.md
new file mode 100644
index 000000000..e0f254566
--- /dev/null
+++ b/.changeset/thin-houses-provide.md
@@ -0,0 +1,5 @@
+---
+'myst-transforms': minor
+---
+
+Sort (frontmatter) abbreviations definitions by length
diff --git a/docs/glossaries-and-terms.md b/docs/glossaries-and-terms.md
index 93c9ef698..b5384f5a3 100644
--- a/docs/glossaries-and-terms.md
+++ b/docs/glossaries-and-terms.md
@@ -70,5 +70,5 @@ The abbreviations are case-sensitive and will replace all instances[^1] in your
 
 :::{tip} Order of Abbreviations
 :class: dropdown
-The order of abbreviations in your frontmatter should specify the longer abbreviations first (e.g. `RHR`) and then the shorter abbreviations (e.g. `HR`). If you do this in the opposite order, you will have an abbreviation for R`HR`.
+Abbreviations defined in your frontmatter are applied in longest-sorted order. If you have two abbreviations with the same suffix (e.g. `RHR` and `HR`), the longer abbreviation will always take precedence.
 :::
diff --git a/packages/myst-transforms/src/abbreviations.ts b/packages/myst-transforms/src/abbreviations.ts
index 0cdf4851d..44c50b422 100644
--- a/packages/myst-transforms/src/abbreviations.ts
+++ b/packages/myst-transforms/src/abbreviations.ts
@@ -26,6 +26,7 @@ function replaceText(mdast: GenericParent, opts: Options) {
   const replacements: FindAndReplaceSchema = Object.fromEntries(
     Object.entries(opts.abbreviations)
       .filter(([abbr]) => abbr.length > 1) // We can't match on single characters!
+      .sort((a, b) => b[0].length - a[0].length || a[0].localeCompare(b[0])) // Sort by length (longest-first) then locale-ordering
       .map(([abbr, title]) => [
         abbr,
         (value: any, { stack }: RegExpMatchObject) => {
@@ -41,6 +42,9 @@ function replaceText(mdast: GenericParent, opts: Options) {
 
 export function abbreviationTransform(mdast: GenericParent, opts?: Options) {
   if (!opts?.abbreviations || Object.keys(opts.abbreviations).length === 0) return;
+
+  // Inline abbreviations have lower priority to passed-in abbreviations
+  // So, we replace conflicting titles with those that have been passed-in
   const abbreviations = selectAll('abbreviation', mdast) as Abbreviation[];
   abbreviations.forEach((node) => {
     if (node.title) return;
@@ -48,6 +52,8 @@ export function abbreviationTransform(mdast: GenericParent, opts?: Options) {
     const title = opts.abbreviations?.[abbr];
     if (title) node.title = title;
   });
+
+  // Replace instances of abbreviated constructs with their titles
   replaceText(mdast, opts);
 
   if (opts.firstTimeLong) {