symbol,sign,mark,signal在词典的解释都是记号或标志,有什么区别?

表示有.的迹象、征兆signal:（报警）信号、红绿灯 A red lamp is often a danger signal比较具体symbol:象征The lion is the symbol of courage 比较抽象mark:分数、做标记The road we should take is marked on the map There are _signs___that a new,different South is coming out of its dark past:有迹象显示一个全新的、与以往不同的南方将要从它黑暗的历史中诞生.3.sign就是标记,预兆,经常是比较具体的现象,但含意很抽象,比如例句：
A high forehead is thought to be a sign of intelligence.
高额头被认为是智慧的标志.
高额头是可以用肉眼直接看到的
sign作动词是签署,例句：
sign a bill into law.
签字批准一项法案.这个跟那两个就差别很明显.
signal是信号,例句：
A red light is usually a signal of danger.
红灯通常是危险的信号.是非常具体的,而且经常是用作专业术语上的,电信号,数字信号等等.
symbol符号,经常也是用作术语,例如：4.sign指"具有一定含义的任何有形或无形的符号或标志,它的表示可以是实物、表情、动作、文字、语言及任何痕迹或征兆",如1)Nodding is a sign of consent.(2)He gave them a sign to withdraw.(3) "Maverick" is my call sign.(4) The old man showed no sign of hearing us.signal 意为“信号,暗号,近因,导火线”,多侧重于声音或动作的暗示,如：(1)The ship is flying a distress signal.(那艘船正在挂起呼救信号）(2)The Lieutenant gave the signal for advance.(尉官做了一个前进的手势） (3)I gave them a tune or two on the piano every now and then making signals to let them know I was alive still and happy.(我时不时地在钢琴上挥洒一两曲,作出信号好让他们知道鄙人依然生龙活虎,兴致如常） symbol记号 符号 象征 表征,如:(1)The dove is a peace symbol.(2)The elephant is the national symbol of Thailand.（大象是泰国的象征） mark指"为某一目的有意作的标记",也指"无意留下或自然形成的痕迹",如:(1)The work he accomplished has left its mark on the contemporary era and will testify eaternally to his exceptional qualities.(他所完成的工作对当代已留下不可磨灭的标记,并将永远成为其非凡品质的见证）(2)You can see in him the marks of an educated man.从他身上你可以看到受过教育的人的特点.operation symbol运算符号punctuation symbol标点符号符号和信号的区别这是语文问题,你可以差一下语文字典.
符号[symbol;sign;mark]∶印记;标号元素符号[insignia]∶用于区分某种特征的标识军衔符号信号[signal]
1经商定作为采取一致行动的时刻的暗号
2一种可以觉察的物理量或脉冲(如电压、电流、磁场强度等),通过它们能传达消息或信息