Complex sentence: A "swingletree" or "singletree" is a special kind of whippletree used for a horse-drawn vehicle, and the term swingletree is sometimes used for draught whippletrees generally.
Split into simpler sentences: A "swingletree", or "singletree", is a special kind of whippletree used for a horse-drawn vehicle. The term swingletree is sometimes used for draught whippletrees generally.