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be a signalman
signalman 是可数名词，指铁路信号员；表示职业时可用 be + a/an + 职业名词。
He is a signalman in the railroad yard.
他是铁路车场的一名信号员。
信号员；铁路信号员
signalmen — plural of signalman
先理解核心含义，再看它在真实句子里的用法。
信号员；铁路信号员
a railroad employee in charge of signals and switches in a railroad yard
He is a signalman in the railroad yard.
他是铁路车场的一名信号员。
负责操作铁路信号和道岔的人。
Somebody employed to operate the signals and points of a railway.
负责发送信号的武装部队成员。
A member of the armed forces responsible for signalling.
通过提供不同视角来指挥索具或起重机操作的人。
Somebody employed to direct rigging or crane operations by providing a different point of view.
The signalman raised the green flag to let the train leave the station.
信号员举起绿旗让火车离站。
Signalmen work in small huts beside the railway tracks.
信号员在铁路旁的信号塔里工作。
The signalman explained how the signals were controlled in the old days.
信号员解释了过去如何控制信号。
signalman 是可数名词，指铁路信号员；表示职业时可用 be + a/an + 职业名词。
He is a signalman in the railroad yard.
他是铁路车场的一名信号员。
signalman 的复数形式是 signalmen，不是 signalmans；与数字连用要用复数形式。
Two signalmen are on duty at the yard.
两名信号员在车场值班。
用 in 短语作后置定语，说明信号员的工作地点。
A signalman in the railroad yard operates the signals.
铁路车场的一名信号员操作信号。
Not this
He is signalman at the railway station.
Use this
He is a signalman at the railway station.
signalman 是可数名词单数，前面需要不定冠词 a。中文没有冠词，容易漏掉；加上 a 后句子才符合英语单数可数名词的规则。
Not this
There are three signalmans at the station.
Use this
There are three signalmen at the station.
signalman 的复数形式是不规则的，要把 man 变成 men，即 signalmen，不能直接在词尾加 -s 写成 signalmans。
Focus on the distinctions below. Other candidates are kept compact until a reliable usage note is available.
铁路信号员
The railroad signalman checked the signals before the train arrived.
铁路信号员在火车到达前检查了信号。
值班信号员
The signalman on duty noticed the red light and stopped the train.
值班信号员注意到红灯，让列车停了下来。
经验丰富的信号员
An experienced signalman can handle several tracks at once.
经验丰富的信号员能同时处理多条轨道。
担任信号员
After his training, he worked as a signalman for twenty years.
培训结束后，他担任了二十年的信号员。
信号长
The chief signalman coordinated all the yard operations.
信号长协调车场的所有作业。
Use signalmen naturally, then get feedback on meaning, tone, grammar, and phrasing.
Revisit a common error or keep this word in your review list.
把 signalman 拆成 signal（信号）+ man（人）：铁路边管信号灯的人，就是信号员。
语域：neutral 常见场景：铁路运营、铁路岗位描述、铁路新闻报道 signalman 通常用于铁路行业，指负责信号和道岔的铁路员工，多出现在正式或职业相关的语境中。口语中较少直接使用。
The final -man in signalman is unstressed and pronounced /mən/, as in gentleman /ˈdʒentlmən/, postman /ˈpoʊstmən/, and policeman /pəˈliːsmən/. Be careful: man /mæn/ and snowman /ˈsnoʊmæn/ keep the full vowel /mæn/, so they do not match the ending sound. The first part signal is the same as the standalone word signal /ˈsɪɡnəl/.
Dictionary facts from ECDICT, WIKTIONARY.