diff --git a/src/string_similarity.h b/src/string_similarity.h
index eb66dd97..51c25208 100644
--- a/src/string_similarity.h
+++ b/src/string_similarity.h
@@ -20,9 +20,15 @@ typedef struct affine_gap_edits {
     size_t num_gap_extensions;
 } affine_gap_edits_t;
 
-affine_gap_edits_t affine_gap_distance(char *s1, char *s2);
+affine_gap_edits_t affine_gap_distance(const char *s1, const char *s2);
 affine_gap_edits_t affine_gap_distance_unicode(uint32_array *u1_array, uint32_array *u2_array);
 
+bool possible_abbreviation(const char *s1, const char *s2);
+bool possible_abbreviation_strict(const char *s1, const char *s2);
+bool possible_abbreviation_unicode(uint32_array *u1_array, uint32_array *u2_array);
+bool possible_abbreviation_unicode_strict(uint32_array *u1_array, uint32_array *u2_array);
+bool possible_abbreviation_unicode_with_edits(uint32_array *u1_array, uint32_array *u2_array, affine_gap_edits_t edits);
+
 ssize_t damerau_levenshtein_distance(const char *s1, const char *s2);
 ssize_t damerau_levenshtein_distance_unicode(uint32_array *u1_array, uint32_array *u2_array, size_t replace_cost);
 ssize_t damerau_levenshtein_distance_replace_cost(const char *s1, const char *s2, size_t replace_cost);