To detect something means to find it or discover that it is present somewhere by using equipment or making an investigation.
例句
...a sensitive piece of equipment used to detect radiation...一件用于探测辐射的灵敏设备Most skin cancers can be cured if detected and treated early...如果早发现早治疗，大多数皮肤癌是可以治愈的。
VERB
觉察;发觉
If you detect something, you notice it or sense it, even though it is not very obvious.
例句
Arnold could detect a certain sadness in the old man's face.阿诺德能觉察到老人脸上的一丝悲伤。