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back and forth
表示两个方向之间的往复运动。
They walked back and forth.
他们来回走动。
出来；出现
先理解核心含义，再看它在真实句子里的用法。
出来；出现
out into view
They walked back and forth.
他们来回走动。
从特定事物、地点或位置出发
from a particular thing or place or position (`forth' is obsolete)
在时间、顺序或程度上向前
forward in time or order or degree
出来；出现
out into view
He went forth into the unknown, determined to find a new life.
他向前迈进，进入未知领域，决心寻找新生活。
The trees put forth new leaves in early spring, signaling the end of winter.
树木在早春长出嫩叶，标志着冬天的结束。
From that day forth, they vowed to always support each other.
从那天起，他们发誓永远互相支持。
表示两个方向之间的往复运动。
They walked back and forth.
他们来回走动。
用于列举末尾，表示还有其他类似项目。
We discussed books, movies, and so forth.
我们讨论了书籍、电影等等。
可以表示提出或陈述观点，也可表示启程（较古语）。
He set forth his ideas clearly.
他清楚地阐述了他的想法。
Not this
He went fourth into the unknown.
Use this
He went forth into the unknown.
同音词混淆：'fourth' 是序数词，而 'forth' 是副词，表示向前或出来。学生常因发音相同而拼错。
Not this
He came forth the room.
Use this
He came out of the room.
介词缺失：'forth' 是副词，不能直接接名词。应使用 'out of' 等介词短语来表达从某处出来。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
来回地，往返地
They walked back and forth.
他们来回走动。
阐述，提出
He set forth his ideas clearly.
他清晰地阐述了自己的想法。
产生，引起
Her speech brought forth a lot of questions.
她的演讲引发了许多问题。
出现，涌现
Several candidates came forth to apply.
几位候选人前来申请。
出发，发布
The order went forth from the headquarters.
命令从总部发出。
滔滔不绝地说
He held forth on the topic for hours.
他就这个话题滔滔不绝地讲了好几个小时。
来回地
The children were running back and forth in the yard.
孩子们在院子里来回跑动。
产生；提出
The investigation brought forth new evidence.
调查提出了新的证据。
等等
She bought apples, oranges, pears, and so forth.
她买了苹果、橘子、梨等等。
把安提阿圣手榴弹拿上来！
The king commanded his knights to bring forth the sacred relic.
国王命令他的骑士们拿出圣物。
前进，不要畏惧黑暗！
The hero rode forth to face his destiny.
英雄骑马前进，去面对他的命运。
Use forth naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
forth 与 fourth 同音，但 forth 表示'向前'，拼写少一个 u。想象向前走时，不需要第四步的停顿。
通常用于较为正式或文学性的语境，在固定搭配（如back and forth）中较为常见。
常与动词搭配使用，如 bring forth, set forth，表示‘向前’或‘出来’，较正式或文学化。
Dictionary facts from ECDICT, WIKTIONARY, WORDNET.