Fix/is correct single token

CHANGELOG.md

@@ -16,6 +16,7 @@ This project follows [Semantic Versioning](https://semver.org/).
 - `with_locale("en")` tries `en`, then `en_US`, then `en_GB`
 - macOS `with_locale` stores the installed language tag that matched, and accepts a bare language when only a regional tag is installed
 - Linux tokenization uses Hunspell `WORDCHARS`/`ICONV`, keeps curly apostrophes in words, trims edge quotes, and skips URLs and emails
+- `is_correct` requires a single whitespace-delimited token with a letter or digit; empty and punctuation-only inputs are false
 
 ## [0.4.0] - 2026-08-25
 

src/lib.rs

@@ -218,8 +218,28 @@ impl Checker {
         self.0.check(text).map(SpellingError)
     }
 
-    /// Returns true if `word` is spelled correctly.
+    /// Returns true if `word` is a single spelled-correctly token.
+    ///
+    /// The input is trimmed. It must be exactly one whitespace-delimited token
+    /// that contains at least one letter or digit. Otherwise this returns
+    /// `false` (empty input, `"!!!"`, `"hello world"`, etc.).
     pub fn is_correct(&self, word: &str) -> bool {
+        let word = word.trim();
+        if word.is_empty() {
+            return false;
+        }
+
+        let mut tokens = word.split_whitespace();
+        let Some(token) = tokens.next() else {
+            return false;
+        };
+        if tokens.next().is_some() {
+            return false;
+        }
+        if !token.chars().any(|c| c.is_alphanumeric()) {
+            return false;
+        }
+
         self.check(word).next().is_none()
     }
 
@@ -540,6 +560,11 @@ mod tests {
         let checker = Checker::with_locale("en_US").unwrap();
         assert!(checker.is_correct("believe"));
         assert!(!checker.is_correct("beleeve"));
+        assert!(!checker.is_correct(""));
+        assert!(!checker.is_correct("   "));
+        assert!(!checker.is_correct("!!!"));
+        assert!(!checker.is_correct("hello world"));
+        assert!(checker.is_correct("  believe  "));
     }
 
     #[test]