signal 来自拉丁语 signale（标志，信号），源自 signum（符号，标记）。核心义项：① 名词：信号，标志（传递信息或指令的标记）；② 名词：迹象，预兆（标志着某种趋势或变化）；③ 动词：发出信号，示意（signal to sb. to do / signal that...）。关键：signal 作为名词（迹象、表明）在议论文中极高频，相当于「这个现象说明了什么」。区别：signal（信号，预兆，暗示某种含义）vs. sign（标志，迹象，更宽泛，可指任何可见标记）vs. indication（迹象，指标，更书面，侧重「数据/证据指向某个结论」）。
释义
1
n.信号，标志（传递信息或指令）
The driver failed to give a signal before turning, causing the cyclist behind to swerve dangerously.
司机在转弯前未打信号，导致后方骑行者危险地急转弯。
2
n.迹象，预兆（表明某种趋势或变化）
The sharp rise in unemployment is a clear signal that the economy is entering a period of contraction.
失业率的急剧上升是经济正进入收缩期的明显迹象。
3
v.发出信号，示意；表明，标志着
The central bank's decision to cut interest rates signals a shift towards a more accommodative monetary policy.
央行降息的决定表明货币政策向更宽松方向转变。
语感
signal = 「注意，我有话说」——可以是具体的物理信号，也可以是事件传递的隐含信息
信号迹象预兆表明（动词）
名词义项二和动词义项在议论文写作中极高频：a signal that...（…的迹象）；signal a change / shift / turning point（标志着变化/转折点）。区别：signal（主动发出的提示，常含「有意传递」之意）vs. sign（更宽泛，可以是自然出现的迹象，不一定有意传递）vs. indication（指标，书面正式，an indication of = 某种迹象，强调数据或事实指向某结论）。固定搭配：signal to sb. to do（示意某人做某事）；give / send a signal（发出信号）。
陷阱
⚠️signal vs. sign：主动发出 vs. 自然出现的迹象
The sudden withdrawal of troops from the border region was seen as a signal of the government's willingness to negotiate.
The government's increased investment in renewable energy sends a clear signal of its commitment to achieving carbon neutrality.
政府对可再生能源的增加投资发出了其致力于实现碳中和的明确信号。
Rising enrolment figures in vocational training programmes are an indication that attitudes towards non-academic pathways are gradually changing.
职业培训项目入学人数的上升是人们对非学术路径态度逐渐改变的迹象。
写作加分
✨ 加分词
替换：showmeanprove
经济政策类议论文社会趋势话题
普通
This shows that the government is changing its policies on education.
这表明政府正在改变其教育政策。
加分 ✨
The government's recent reforms signal a fundamental shift in its approach to education, prioritising skills development over academic achievement.
政府近期的改革表明其教育方式发生了根本性转变，将技能发展置于学业成绩之上。
为什么更好：signal a fundamental shift 比 show a change 更书面，含「有意传递政策方向」的语义，配合 prioritising...over 对比结构，论证更具分析深度
常用搭配
signal a change / shift / turning point标志着变化 / 转变 / 转折点
give / send a signal发出信号
signal to sb. to do sth.示意某人做某事
a clear / strong signal明确 / 强烈的信号
a warning signal / signal of danger警示信号 / 危险信号
词根
signal = sign（标记）+ al → 带有标记作用的 = 信号，迹象
考考你
Q1义项辨析
下面四个句子中，signal 的用法与其他三个最不同的是：
A
The traffic lights signalled green, allowing the pedestrians to cross safely.
交通灯亮起绿灯，允许行人安全过马路。
B
The declining birth rate signals a deeper demographic crisis that will challenge pension systems for decades.
出生率下降标志着一场更深层的人口危机，这将给养老金制度带来数十年的挑战。
C
The coach signalled to the substitute player to warm up and prepare to enter the field.
教练示意替补球员热身并准备上场。
D
The sudden drop in consumer spending signals that households are growing increasingly cautious about the economic outlook.
消费支出的骤然下降表明家庭对经济前景日益谨慎。
Q2近义选词
选择最恰当的词填空：
A sudden increase in the number of vacant retail units on the high street is a strong ___ that consumer spending in the area has declined significantly.
The passing of legislation in multiple countries to restrict children's data collection by social media platforms signals a significant shift in governments' approach to digital regulation.
关键搭配：signals a significant shift
signal a significant shift（标志着重大转变）是议论文描述政策趋势的核心书面动词搭配，比 show a change 更书面，含「有意传递政策方向」的语义
接着学
点击进入该词的深度解析
sign近义迹象，标志（更宽泛，可以是自然出现的，不一定有意传递，a sign of improvement = 好转的迹象）
symptom近义症状；表征（多用于医学或隐喻「社会问题的症状」，a symptom of a larger problem = 更大问题的症状）
gesture近义姿态，手势（signal to sb. 可以是 gesture，但 gesture 更强调「身体动作」或「象征性行为」）