核心问题
My new house is half as large again as my old one.
[原译]我的新房子是我的旧房的一半大。(《最新高级英汉词典》,商务印书馆,1995年,p.18)
如果 A is half as large again as B 真是指“A 是 B 的一半大”，那么 A is half as large as B 又是什么意思呢？难道它们是同义表达手段吗？
词典解答
看来，上面的误译不是因疏忽造成的，而是因误解造成的。A is n times as large(much, many, long, tall) as B 意为 A 是 B 的 n 倍大(多、长、高)，因此，A is half as large(much, many, long, tall) 意为 A 是 B 的一半大(多、长、高)。A is n times(half) as large(much, many, long, tall) again 则是 A 比 B 大(多、长、高)n 倍(一半)，可见，有无 again，意思截然不同，请看下面的实例：
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These shoes cost me as much again as the last pair I bought. (Whitford) 买这双鞋比上次买的那双鞋多花了一倍的钱。
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We have turned out half as much coal again as they. 我们出产的煤比他们多半倍。
(参见 as much as, as many/as many again)