Chapter 1: Hesitant Fuzzy Set.- Chapter 2: Hesitant Fuzzy Linguistic Term Set.- Chapter 3: Neutrosophic Hesitant Fuzzy Set.- Chapter 4: Pythagorean Hesitant Fuzzy Set.- Chapter 5: q-Rung Orthopair Hesitant Fuzzy Set.- Chapter 6: Probabilistic Hesitant Fuzzy Set.- Chapter 7: Type 2 Hesitant Fuzzy Set.- Chapter 8: Hesitant Bipolar Fuzzy Set.- Chapter 9: Cubic Hesitant Fuzzy Set.- Chapter 10: Complex Hesitant Fuzzy Set.- Chapter 11: Picture Hesitant Fuzzy Set.- Chapter 12: Spherical Hesitant Fuzzy Set.