diff --git a/phino.cabal b/phino.cabal
--- a/phino.cabal
+++ b/phino.cabal
@@ -1,7 +1,7 @@
 cabal-version:      3.0
 
 name:               phino
-version:            0.0.0.28
+version:            0.0.0.29
 license:            MIT
 synopsis:           Command-Line Manipulator of 𝜑-Calculus Expressions
 description:        Please see the README on GitHub at <https://github.com/objectionary/phino#readme>
diff --git a/src/Functions.hs b/src/Functions.hs
--- a/src/Functions.hs
+++ b/src/Functions.hs
@@ -114,4 +114,8 @@
   str <- randomString pat
   pure (TeExpression (DataString (strToBts str)))
 buildTermFromFunction "random-string" _ _ _ = throwIO (userError "Function random-string() requires exactly 1 dataizable argument")
+buildTermFromFunction "size" [ArgBinding (BiMeta meta)] subst _ = do
+  bds <- buildBindingThrows (BiMeta meta) subst
+  pure (TeExpression (DataNumber (numToBts (fromIntegral (length bds)))))
+buildTermFromFunction "size" _ _ _ = throwIO (userError "Function size() requires exactly 1 meta binding")
 buildTermFromFunction func _ _ _ = throwIO (userError (printf "Function %s() is not supported or does not exist" func))