diff --git a/src/api/vocabApi.js b/src/api/vocabApi.js
new file mode 100644
index 0000000..4de64ec
--- /dev/null
+++ b/src/api/vocabApi.js
@@ -0,0 +1,30 @@
+import axios from 'axios'
+
+const vocabApi = axios.create({
+  baseURL: import.meta.env.VITE_VOCAB_API_URL,
+  timeout: 10000,
+  headers: {
+    'Content-Type': 'application/json',
+  },
+})
+
+// Request interceptor
+vocabApi.interceptors.request.use(
+  (config) => {
+    return config
+  },
+  (error) => {
+    return Promise.reject(error)
+  }
+)
+
+// Response interceptor
+vocabApi.interceptors.response.use(
+  (response) => response.data,
+  (error) => {
+    console.error('Vocab API Error:', error.response?.data || error.message)
+    return Promise.reject(error)
+  }
+)
+
+export default vocabApi
diff --git a/src/domains/vocab/constants/vocabConstants.js b/src/domains/vocab/constants/vocabConstants.js
new file mode 100644
index 0000000..60484e8
--- /dev/null
+++ b/src/domains/vocab/constants/vocabConstants.js
@@ -0,0 +1,95 @@
+// 학습 레벨
+export const LEVELS = {
+  BEGINNER: 'BEGINNER',
+  INTERMEDIATE: 'INTERMEDIATE',
+  ADVANCED: 'ADVANCED',
+}
+
+export const LEVEL_LABELS = {
+  [LEVELS.BEGINNER]: '초급',
+  [LEVELS.INTERMEDIATE]: '중급',
+  [LEVELS.ADVANCED]: '고급',
+}
+
+export const LEVEL_COLORS = {
+  [LEVELS.BEGINNER]: 'success',
+  [LEVELS.INTERMEDIATE]: 'warning',
+  [LEVELS.ADVANCED]: 'error',
+}
+
+// 카테고리
+export const CATEGORIES = {
+  DAILY: 'DAILY',
+  BUSINESS: 'BUSINESS',
+  ACADEMIC: 'ACADEMIC',
+}
+
+export const CATEGORY_LABELS = {
+  [CATEGORIES.DAILY]: '일상',
+  [CATEGORIES.BUSINESS]: '비즈니스',
+  [CATEGORIES.ACADEMIC]: '학술',
+}
+
+// 학습 상태
+export const WORD_STATUS = {
+  NEW: 'NEW',
+  LEARNING: 'LEARNING',
+  REVIEWING: 'REVIEWING',
+  MASTERED: 'MASTERED',
+}
+
+export const WORD_STATUS_LABELS = {
+  [WORD_STATUS.NEW]: '새 단어',
+  [WORD_STATUS.LEARNING]: '학습 중',
+  [WORD_STATUS.REVIEWING]: '복습 중',
+  [WORD_STATUS.MASTERED]: '암기 완료',
+}
+
+export const WORD_STATUS_COLORS = {
+  [WORD_STATUS.NEW]: 'default',
+  [WORD_STATUS.LEARNING]: 'warning',
+  [WORD_STATUS.REVIEWING]: 'info',
+  [WORD_STATUS.MASTERED]: 'success',
+}
+
+// 난이도
+export const DIFFICULTY = {
+  EASY: 'EASY',
+  NORMAL: 'NORMAL',
+  HARD: 'HARD',
+}
+
+export const DIFFICULTY_LABELS = {
+  [DIFFICULTY.EASY]: '쉬움',
+  [DIFFICULTY.NORMAL]: '보통',
+  [DIFFICULTY.HARD]: '어려움',
+}
+
+// 시험 유형
+export const TEST_TYPES = {
+  KOREAN_TO_ENGLISH: 'KOREAN_TO_ENGLISH',
+  ENGLISH_TO_KOREAN: 'ENGLISH_TO_KOREAN',
+}
+
+export const TEST_TYPE_LABELS = {
+  [TEST_TYPES.KOREAN_TO_ENGLISH]: '한국어 → 영어',
+  [TEST_TYPES.ENGLISH_TO_KOREAN]: '영어 → 한국어',
+}
+
+// TTS 음성
+export const VOICE_TYPES = {
+  MALE: 'MALE',
+  FEMALE: 'FEMALE',
+}
+
+export const VOICE_LABELS = {
+  [VOICE_TYPES.MALE]: '남성',
+  [VOICE_TYPES.FEMALE]: '여성',
+}
+
+// 일일 학습 목표
+export const DAILY_GOAL = {
+  NEW_WORDS: 50,
+  REVIEW_WORDS: 5,
+  TOTAL: 55,
+}
diff --git a/src/domains/vocab/index.js b/src/domains/vocab/index.js
new file mode 100644
index 0000000..05c63ec
--- /dev/null
+++ b/src/domains/vocab/index.js
@@ -0,0 +1,5 @@
+// Services
+export * from './services/vocabService'
+
+// Constants
+export * from './constants/vocabConstants'
diff --git a/src/domains/vocab/services/vocabService.js b/src/domains/vocab/services/vocabService.js
new file mode 100644
index 0000000..1014b98
--- /dev/null
+++ b/src/domains/vocab/services/vocabService.js
@@ -0,0 +1,91 @@
+import vocabApi from '../../../api/vocabApi'
+
+/**
+ * 단어 관리 API (#65)
+ */
+export const wordService = {
+  // 단어 목록 조회
+  getList: ({ level, category, limit = 20, cursor } = {}) =>
+    vocabApi.get('/vocab/words', { params: { level, category, limit, cursor } }),
+
+  // 단어 검색
+  search: ({ q, limit = 20, cursor } = {}) =>
+    vocabApi.get('/vocab/words/search', { params: { q, limit, cursor } }),
+
+  // 단어 상세 조회
+  getDetail: (wordId) =>
+    vocabApi.get(`/vocab/words/${wordId}`),
+}
+
+/**
+ * 일일 학습 API (#66)
+ */
+export const dailyService = {
+  // 오늘의 학습 단어 조회
+  getWords: (userId) =>
+    vocabApi.get(`/vocab/daily/${userId}`),
+
+  // 단어 학습 완료 표시
+  markLearned: (userId, wordId, isCorrect) =>
+    vocabApi.post(`/vocab/daily/${userId}/words/${wordId}/learned`, { isCorrect }),
+}
+
+/**
+ * 사용자 단어 학습 상태 API (#67)
+ */
+export const userWordService = {
+  // 학습 상태 조회
+  getList: (userId, { status, limit = 20, cursor } = {}) =>
+    vocabApi.get(`/vocab/users/${userId}/words`, { params: { status, limit, cursor } }),
+
+  // 학습 결과 업데이트 (정답/오답)
+  update: (userId, wordId, isCorrect) =>
+    vocabApi.put(`/vocab/users/${userId}/words/${wordId}`, { isCorrect }),
+
+  // 단어 태그 변경 (북마크/즐겨찾기/난이도)
+  updateTag: (userId, wordId, { bookmarked, favorite, difficulty }) =>
+    vocabApi.put(`/vocab/users/${userId}/words/${wordId}/tag`, { bookmarked, favorite, difficulty }),
+}
+
+/**
+ * 시험 API (#68)
+ */
+export const testService = {
+  // 시험 시작
+  start: (userId, { wordCount = 20, level, type = 'ENGLISH_TO_KOREAN' } = {}) =>
+    vocabApi.post(`/vocab/test/${userId}/start`, { wordCount, level, type }),
+
+  // 답안 제출
+  submit: (userId, testId, answers) =>
+    vocabApi.post(`/vocab/test/${userId}/submit`, { testId, answers }),
+
+  // 시험 결과 조회
+  getResults: (userId, { limit = 20, cursor } = {}) =>
+    vocabApi.get(`/vocab/test/${userId}/results`, { params: { limit, cursor } }),
+}
+
+/**
+ * 통계 API (#69)
+ */
+export const statsService = {
+  // 전체 학습 통계
+  getOverall: (userId) =>
+    vocabApi.get(`/vocab/stats/${userId}`),
+
+  // 일별 학습 통계
+  getDaily: (userId, { limit = 30 } = {}) =>
+    vocabApi.get(`/vocab/stats/${userId}/daily`, { params: { limit } }),
+
+  // 약점 분석
+  getWeakness: (userId) =>
+    vocabApi.get(`/vocab/stats/${userId}/weakness`),
+}
+
+/**
+ * 음성 API (TTS) (#70)
+ */
+export const voiceService = {
+  // 단어 발음 합성
+  synthesize: (wordId, text, voice = 'FEMALE') =>
+    vocabApi.post('/vocab/voice/synthesize', { wordId, text, voice }),
+}