turn-about和about-turn有何分別?

Turn about 和 about turn 都是解作一百ハ十度調轉頭，不過也有不同的地方：
Turn about 和 turn around 一樣，可以解原地調轉頭，或向前作一個圓圈式的調頭。About turn 只是指原地一百ハ十度自轉，尤其是作軍操時用。
Turn about 是 idiom，是個 verb phrase。About turn 是個 noun。所以文法上運用不同。
例子：
(1) The solders marched forward 100 meters, stopped, made an about turn and marched back to the starting point.
(2) "Turn about so I can see you".
(3) "You have missed it. Turn the car about and drive for about 2 miles; after you have crossed the bridge, make a right turn and you will see it."

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