Difference Between Fuse & Detector

Page 34, Elementary Electrical Terms, Vol II.

Well I can clearly see that English syntax and grammar is not your strong suit. I guess that is why you do not understand how to use a dictionary or search engine for what, at first, seems to be a ridiculously trivial question. To try and answer your question I must make a few assumptions due to the imprecision of your text.

What a fuse and contactor have in common in electrical engineering is that they both interrupt current flow. The difference is when they interrupt this current. A contactor does this under normal operating conditions and as such is expected to do this many times because the current magnitude will be understood. A fuse interrupts current under a fault condition and therefore the current interrupted will be unknown. Since a failure operating condition produces an unknown current condition, a fuse is designed to produce a controlled failure in itself. This prevents a more catastrophic failure in something else that may start a fire, explosion or a variety of other dangerous conditions.