The word 疲倦 (píjuàn) is a compound formed by combining two synonymous characters, each contributing to the overall meaning of fatigue. The first character, 疲 (pí), primarily conveys a sense of physical weariness or exhaustion, while the second, 倦 (juàn), leans more toward mental tiredness, boredom, or a state of being wearied. When paired together in this common parallel structure in Chinese vocabulary, they create a more comprehensive and nuanced term that encompasses both the physical and mental dimensions of being thoroughly tired or fatigued.