diff --git a/src/common/fluentVowels.ts b/src/common/fluentVowels.ts
index 5496dd2..8df18b8 100644
--- a/src/common/fluentVowels.ts
+++ b/src/common/fluentVowels.ts
@@ -1,7 +1,4 @@
-import { ALL_CHARACTERS, CONSONANT_CHARACTERS } from '../constants';
-
-const LETTERS = new Set(ALL_CHARACTERS);
-const CONSONANTS = new Set(CONSONANT_CHARACTERS);
+import { ALL_LETTERS, ALL_CONSONANTS } from '../substitutions';
 
 export function markFluentVowel(word: string, add: string): string {
   let i = 0;
@@ -26,7 +23,7 @@ export function inferFluentVowel(word: string): string {
 
   while (i > 0) {
     const char = word[i];
-    if (!LETTERS.has(char)) {
+    if (!ALL_LETTERS.has(char)) {
       end = i;
       replaced = false;
     }
@@ -53,7 +50,7 @@ function replaceFluentVowel(word: string, j: number): string {
 }
 
 function isLastSyllable(word: string, i: number, end: number): boolean {
-  if (i === end - 2) return CONSONANTS.has(word[i + 1]);
+  if (i === end - 2) return ALL_CONSONANTS.has(word[i + 1]);
   if (i === end - 3) return word[i + 1] === 'n' && word[i + 2] === 'j';
   return false;
 }
diff --git a/src/constants/alphabet.ts b/src/constants/alphabet.ts
deleted file mode 100644
index 1bae862..0000000
--- a/src/constants/alphabet.ts
+++ /dev/null
@@ -1,5 +0,0 @@
-export {
-  ALL_CHARACTERS,
-  CONSONANT_CHARACTERS,
-  VOWEL_CHARACTERS,
-} from '../substitutions';
diff --git a/src/constants/index.ts b/src/constants/index.ts
index 47771c4..acfa977 100644
--- a/src/constants/index.ts
+++ b/src/constants/index.ts
@@ -1,3 +1,2 @@
-export * from './alphabet';
 export * from './bcp47';
 export * from './glagolitic';
diff --git a/src/noun/declensionNoun.ts b/src/noun/declensionNoun.ts
index 8838dd8..d170f27 100644
--- a/src/noun/declensionNoun.ts
+++ b/src/noun/declensionNoun.ts
@@ -5,10 +5,11 @@
 import { declensionAdjective } from '../adjective';
 import { inferFluentVowel, markFluentVowel } from '../common';
 import type { Noun } from '../partOfSpeech';
-import { matchEnd, removeBrackets, replaceStringAt } from '../utils';
+import { removeBrackets, replaceStringAt } from '../utils';
 import { establishGender } from './establishGender';
 
-const AEEO = ['a', 'e', 'ę', 'o'];
+// endings like -i, -u are not declinable usually
+const AEEO$ = /[aeęo]$/;
 
 export function declensionNounFlat(
   rawNoun: string,
@@ -189,7 +190,7 @@ function establish_root(noun: string, gender: string) {
     noun.lastIndexOf('ȯ'),
   );
 
-  const hasVowelEnding = matchEnd(noun, [AEEO]);
+  const hasVowelEnding = AEEO$.test(noun);
 
   if (noun == 'lėv' || noun == 'lev') {
     result = 'ljv';
@@ -283,7 +284,7 @@ function nominative_sg(noun: string, root: string, gender: string) {
   if (gender == 'f2') {
     result = root;
   }
-  if (gender == 'f3' && root.lastIndexOf('v') == root.length - 1) {
+  if (gender == 'f3' && root.endsWith('v')) {
     result = root.substring(0, root.length - 1) + 'ȯv';
   } else if (gender == 'f3') {
     result = noun;
@@ -361,7 +362,7 @@ function instrumental_sg(root: string, gender: string) {
     result = root + 'ojų';
   } else if (gender == 'f2') {
     result = root + 'jų';
-  } else if (gender == 'f3' && root.lastIndexOf('v') == root.length - 1) {
+  } else if (gender == 'f3' && root.endsWith('v')) {
     result = root.substring(0, root.length - 1) + 'ȯvjų';
   } else if (gender == 'f3') {
     result = root + 'jų';
diff --git a/src/substitutions.ts b/src/substitutions.ts
index b43448a..d667120 100644
--- a/src/substitutions.ts
+++ b/src/substitutions.ts
@@ -1,19 +1,16 @@
-export const ALL_CHARACTERS =
-  'aáàăâåąāæbcćçčdďđḓeéèĕêěëėęēǝfghiíìĭîīıjĵklĺľļłŀljmnńňñņnjoóòŏôöȯǫœpqrŕṙřsśšŠtťṱuúùŭûůũųūvwxyýzźżž'.split(
-    '',
-  );
+export const ALL_LETTERS = new Set(
+  'aáàăâåąāæbcćçčdďđḓeéèĕêěëėęēǝfghiíìĭîīıjĵklĺľļłŀljmnńňñņnjoóòŏôöȯǫœpqrŕṙřsśšŠtťṱuúùŭûůũųūvwxyýzźżž',
+);
 
-export const ANY = ALL_CHARACTERS;
+export const ALL_CONSONANTS = new Set(
+  'bcćçčdďđḓfghklĺľļłŀljmnńňñņnjpqrŕṙřsśštťṱvwxzźżž',
+);
 
-export const CONSONANT_CHARACTERS =
-  'bcćçčdďđḓfghklĺľļłŀljmnńňñņnjpqrŕṙřsśštťṱvwxzźżž'.split('');
+export const ALL_VOWELS = new Set(
+  'aáàăâåąāæeéèĕêěëėęēǝiíìĭîīıoóòŏôöȯǫœuúùŭûůũųūyý',
+);
 
-export const CONSONANT = CONSONANT_CHARACTERS;
-
-export const VOWEL_CHARACTERS =
-  'aáàăâåąāæeéèĕêěëėęēǝiíìĭîīıoóòŏôöȯǫœuúùŭûůũųūyý'.split('');
-
-export const VOWEL = VOWEL_CHARACTERS;
+export const VOWELS = new Set('aåeęěėioȯuųy');
 
 export const LJ_NJ = ['lj', 'nj'];
 export const LJj_NJj = ['lj', 'ĺj', 'ľj', 'lj', 'nj', 'ńj', 'ňj', 'ñj', 'nj'];
diff --git a/src/utils/index.ts b/src/utils/index.ts
index bb2b3ac..86ed9d6 100644
--- a/src/utils/index.ts
+++ b/src/utils/index.ts
@@ -1,7 +1,5 @@
 export * from './areArraysEqual';
 export * from './compactArray';
-export * from './matchStart';
-export * from './matchEnd';
 export * from './memoizeLastCall';
 export * from './removeBrackets';
 export * from './replaceStringAt';
diff --git a/src/utils/matchEnd.test.ts b/src/utils/matchEnd.test.ts
deleted file mode 100644
index 25b267b..0000000
--- a/src/utils/matchEnd.test.ts
+++ /dev/null
@@ -1,25 +0,0 @@
-import { matchEnd } from './matchEnd';
-
-describe('matchEnd', () => {
-  it('should return ending when the string ends with the given suffix array', () => {
-    expect(matchEnd('dělati', [['e', 'ě'], 'lat', ['i', 'ı']])).toBe('ělati');
-  });
-
-  it('should return empty string when the string ends with an empty suffix array', () => {
-    expect(matchEnd('', [])).toBe('');
-  });
-
-  it('should return empty string when the string does not match any suffix array', () => {
-    expect(matchEnd('dělåti', [['ě', 'e'], 'lat', ['i', 'ı']])).toBe('');
-  });
-
-  it('should pick first working suffix among others', () => {
-    expect(matchEnd('abcdefg', ['de', ['fg', 'g']])).toBe('defg');
-    expect(matchEnd('abcdefg', ['de', ['g', 'fg']])).toBe('');
-  });
-
-  it('should optimize for single suffix array and single string', () => {
-    expect(matchEnd('dělati', ['i'])).toBe('i');
-    expect(matchEnd('dělati', 'ti')).toBe('ti');
-  });
-});
diff --git a/src/utils/matchEnd.ts b/src/utils/matchEnd.ts
deleted file mode 100644
index 6f6dde3..0000000
--- a/src/utils/matchEnd.ts
+++ /dev/null
@@ -1,51 +0,0 @@
-export function matchEnd(
-  str: string,
-  suffixes: string | Array<string | string[]>,
-): string {
-  if (!Array.isArray(suffixes)) {
-    return str.endsWith(suffixes) ? suffixes : '';
-  }
-
-  if (suffixes.length === 1 && !Array.isArray(suffixes[0])) {
-    return matchEnd(str, suffixes[0]);
-  }
-
-  const S = suffixes.length;
-  let end = str.length;
-  let ending = '';
-
-  for (let k = S - 1; k >= 0; k--) {
-    const start = findSuffixesIndex(str, suffixes[k], end);
-    if (start === -1) {
-      return '';
-    }
-
-    ending = str.slice(start, end) + ending;
-    end = start;
-  }
-
-  return ending;
-}
-
-function findSuffixesIndex(
-  str: string,
-  suffixes: string | string[],
-  end: number,
-): number {
-  let cache = '';
-  let len = 0;
-
-  const arr = Array.isArray(suffixes) ? suffixes : [suffixes];
-  for (const s of arr) {
-    if (len !== s.length) {
-      len = s.length;
-      cache = str.slice(end - len, end);
-    }
-
-    if (cache === s) {
-      return end - len;
-    }
-  }
-
-  return -1;
-}
diff --git a/src/utils/matchStart.test.ts b/src/utils/matchStart.test.ts
deleted file mode 100644
index 1e1f8fc..0000000
--- a/src/utils/matchStart.test.ts
+++ /dev/null
@@ -1,36 +0,0 @@
-import { matchStart } from './matchStart';
-
-describe('matchStart', () => {
-  it('should return beginning when the string starts with the given prefix array', () => {
-    expect(matchStart('dělati', ['d', ['e', 'ě'], 'l'])).toBe('děl');
-  });
-
-  it('should return empty string when the string starts with an empty prefix array', () => {
-    expect(matchStart('', [])).toBe('');
-  });
-
-  it('should return empty string when the string does not match any prefix array', () => {
-    expect(matchStart('dělåti', [['ě', 'e'], 'lat', ['i', 'ı']])).toBe('');
-  });
-
-  it('should pick first working prefix among others', () => {
-    expect(
-      matchStart('abcdefg', [
-        ['ab', 'a'],
-        ['b', 'cd'],
-      ]),
-    ).toBe('abcd');
-
-    expect(
-      matchStart('abcdefg', [
-        ['a', 'ab'],
-        ['b', 'cd'],
-      ]),
-    ).toBe('ab');
-  });
-
-  it('should optimize for single prefix array and single string', () => {
-    expect(matchStart('dělati', ['dě'])).toBe('dě');
-    expect(matchStart('dělati', 'děl')).toBe('děl');
-  });
-});
diff --git a/src/utils/matchStart.ts b/src/utils/matchStart.ts
deleted file mode 100644
index 7f5a9ae..0000000
--- a/src/utils/matchStart.ts
+++ /dev/null
@@ -1,51 +0,0 @@
-export function matchStart(
-  str: string,
-  prefixes: string | Array<string | string[]>,
-): string {
-  if (!Array.isArray(prefixes)) {
-    return str.startsWith(prefixes) ? prefixes : '';
-  }
-
-  if (prefixes.length === 1 && !Array.isArray(prefixes[0])) {
-    return matchStart(str, prefixes[0]);
-  }
-
-  const P = prefixes.length;
-  let start = 0;
-  let prefix = '';
-
-  for (let k = 0; k < P; k++) {
-    const end = findPrefixesIndex(str, prefixes[k], start);
-    if (end === -1) {
-      return '';
-    }
-
-    prefix += str.slice(start, end);
-    start = end;
-  }
-
-  return prefix;
-}
-
-function findPrefixesIndex(
-  str: string,
-  prefixes: string | string[],
-  start: number,
-): number {
-  let cache = '';
-  let len = 0;
-
-  const arr = Array.isArray(prefixes) ? prefixes : [prefixes];
-  for (const p of arr) {
-    if (len !== p.length) {
-      len = p.length;
-      cache = str.slice(start, start + len);
-    }
-
-    if (cache === p) {
-      return start + len;
-    }
-  }
-
-  return -1;
-}
diff --git a/src/verb/conjugationVerb.ts b/src/verb/conjugationVerb.ts
index d0e5db2..14d0d4d 100644
--- a/src/verb/conjugationVerb.ts
+++ b/src/verb/conjugationVerb.ts
@@ -2,17 +2,18 @@
  * @source http://steen.free.fr/interslavic/conjugator.html
  */
 
-import { compactArray, matchEnd } from '../utils';
+import { compactArray } from '../utils';
 import { parsePos, Verb } from '../partOfSpeech';
-import {
-  BIG_YUS,
-  BIG_YUS_LOOSE,
-  IOTATED_SMALL_YUS,
-  SMALL_YUS,
-} from '../substitutions';
+import { BIG_YUS, IOTATED_SMALL_YUS, SMALL_YUS } from '../substitutions';
 
-const _SE = [' se', ' se'];
-const SE_ = ['sę ', 'se '];
+const _SE = /. s[eę]$/;
+const SE_ = /s[eę] $/;
+const EVA_OVA = /[eo]va$/;
+const NUU = /..n[uų]$/;
+const OUEE = /^..?[eěou]$/;
+const BDSZE = /[bdsz]ję$/;
+const AEE = /[aeě]$/;
+const MEUU = /[meuų-]$/;
 
 const PREFIXES = [
   'prědpo',
@@ -48,16 +49,7 @@ const PREFIXES = [
   'v',
 ];
 
-const NON_REGULAR_VERBS = [
-  'věděti',
-  'vedeti',
-  'jesti',
-  'jěsti',
-  'dati',
-  'dųti',
-  'byti',
-  'žegti',
-];
+const NON_REGULAR_VERBS = /(v[eě]d[eě]ti|j[eě]sti|d[aų]ti|byti|žegti)$/;
 
 const irregular_stems = { da: 1, je: 1, jě: 1, ja: 1, vě: 1 };
 
@@ -253,9 +245,9 @@ function splitReflexive(inf: string) {
 
 function prefix(inf: string) {
   // get prefixes for some non-regular verbs
-  const irregular = matchEnd(inf, [NON_REGULAR_VERBS]);
-  if (irregular) {
-    const maybePrefix = inf.slice(0, -irregular.length);
+  const match = inf.match(NON_REGULAR_VERBS);
+  if (match) {
+    const maybePrefix = inf.slice(0, -match[1].length);
     if (PREFIXES.includes(maybePrefix)) {
       return maybePrefix;
     }
@@ -370,13 +362,13 @@ function derive_present_tense_stem(infinitive_stem_string: string): string {
     result = 'uměĵ';
   } else if (result === 'hova') {
     result = 'hovaĵ';
-  } else if (matchEnd(result, [['o', 'e'], 'va'])) {
+  } else if (EVA_OVA.test(result)) {
     result = result.slice(0, -3) + 'uj';
-  } else if (result.length > 3 && matchEnd(result, ['n', BIG_YUS_LOOSE])) {
+  } else if (NUU.test(result)) {
     result = result.slice(0, -1);
-  } else if (result.length < 4 && matchEnd(result, [['o', 'u', 'e', 'ě']])) {
+  } else if (OUEE.test(result)) {
     result = result + 'j';
-  } else if (matchEnd(result, [['b', 'd', 's', 'z'], IOTATED_SMALL_YUS])) {
+  } else if (BDSZE.test(result)) {
     result = result.slice(0, -2) + 'ȯjm';
   } else if (result.endsWith(IOTATED_SMALL_YUS)) {
     result = result.slice(0, -1) + 'm';
@@ -386,7 +378,7 @@ function derive_present_tense_stem(infinitive_stem_string: string): string {
     result = result.slice(0, -1) /*+ 'm'*/;
   } else if (result.endsWith('y')) {
     result = result + 'j';
-  } else if (matchEnd(result, [['a', 'e', 'ě']])) {
+  } else if (AEE.test(result)) {
     result = result + 'ĵ';
   }
   return result;
@@ -398,9 +390,9 @@ function present_tense_stem(pref: string, pts: string, is: string) {
   if (pts.length == 0) {
     result = derive_present_tense_stem(is);
   } else {
-    if (matchEnd(pts, _SE) && pts.length > 3) {
+    if (_SE.test(pts)) {
       pts = pts.slice(0, -3);
-    } else if (matchEnd(pts, SE_)) {
+    } else if (SE_.test(pts)) {
       pts = pts.slice(3);
     }
 
@@ -412,7 +404,7 @@ function present_tense_stem(pref: string, pts: string, is: string) {
       }
     }
 
-    if (matchEnd(pts, [['-', 'm', 'e', 'ų', 'u']])) {
+    if (MEUU.test(pts)) {
       result = pts.slice(0, -1);
     } else {
       result = pts;