Complex sentence: The term "thujene" usually refers to α-thujene, a less common chemically-related double-bond isomer is known as β-thujene (or 2-thujene).
Split into simpler sentences: The term "thujene" usually refers to α-thujene. A less common chemically-related double-bond isomer is known as β-thujene (or 2-thujene).