1
There is a cam in/on + noun
there be 句型用于说明某处存在某物，冠词用 a/an。
There is a cam on the shaft.
轴上有一个凸轮。
剑河
先理解核心含义，再看它在真实句子里的用法。
剑河
a river in east central England that flows past Cambridge to join the Ouse River
There is a cam on the shaft.
轴上有一个凸轮。
A turning or sliding piece which imparts motion to a rod, lever or block brought into sliding or rolling contact with it.
在电影院里非法录制的电影。
A bootleg recording of a film recorded in a movie theater.
英格兰中东部的一条河流,流经剑桥后汇入乌斯河
a river in east central England that flows past Cambridge to join the Ouse River
A spring-loaded camming device, a spring-loaded device for effecting a temporary belay in a rock crevice.
The Cam flows gently through the city of Cambridge.
剑河缓缓地流经剑桥市。
My family rented a rowboat and spent an hour on the Cam.
我们一家租了一条划艇，在剑河上玩了一个小时。
If you stay near the Cam, you can hear birds singing in the morning.
如果你住在剑河附近，早晨就能听到鸟鸣。
there be 句型用于说明某处存在某物，冠词用 a/an。
There is a cam on the shaft.
轴上有一个凸轮。
定冠词 the 特指已知或前述的凸轮，后接动词及宾语。
The cam opens the valve.
凸轮打开阀门。
复数 cams 表示类别，be used to do 意为“被用来做…”。
Cams are used to convert motion.
凸轮用于转换运动。
Not this
Cam is a river in England.
Use this
The Cam is a river in England.
英语中河流名称前通常要加定冠词 the，例如 the Thames、the Cam。汉语没有冠词，学习者容易遗漏，因此应补上 the。
Not this
We took a walk along Cam River.
Use this
We took a walk along the River Cam.
英语中许多英国河名采用“the River + 专名”的语序，如 the River Cam，而不是“Cam River”这种名词叠加形式。汉语“剑河”的语序容易造成迁移错误。
Not this
I cam to the party last night.
Use this
I came to the party last night.
come 的过去式是 came，不是 cam。英语中 came 读 /keɪm/，而 cam 读 /kæm/，汉语学习者常因发音混淆而拼写错误，注意区分字母组合 am 和 ame。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
剑河
We took a walk along the River Cam.
我们沿着剑河散步。
在剑河撑船
Tourists love to punt on the Cam during summer.
游客喜欢在夏天到剑河撑船。
剑河河岸
The banks of the Cam are lined with college buildings.
剑河河岸两旁学院建筑林立。
乘船游览剑河
We went on a boat trip on the Cam to see the colleges.
我们乘船游览剑河，欣赏各学院的风光。
剑河纤道
We cycled along the Cam towpath from Cambridge to Grantchester.
我们沿着剑河纤道从剑桥骑车到格兰切斯特。
Use cam naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
cam 是 camera（相机）的开头：镜头凸起像凸轮，记住凸轮是 cam。
语域：neutral 常见场景：geography、travel、history 根据给出的英文释义，cam 指英格兰的剑河（River Cam），为专有名词，通常首字母大写，多用于地理、旅游或历史语境。
这些词与 cam 的重读元音 /æ/ 和尾音 /m/ 相同，都押韵：ham、jam、ram、yam、dam、lamb。注意 lamb 的 -mb 中 b 不发音。拼写像但读音不同的常见词有 came /keɪm/、calm /kɑːm/、comb /koʊm/，不要按 -am 读。
Dictionary facts from ECDICT, WIKTIONARY.