I came across a sentence from LongMan dictionary while I was looking up the word "fence", and the phrase example was: a structure made of wood, metal etc that surrounds a piece of land. my question is: why the sentence wouldn't be: a structure IS made of wood,... "is made of wood" instead of "made of wood" since we talk about passive voice?!! please explain to me that issue..
A fence is a structure made of wood means the same thing as
A fence is a wooden structure.
In the dictionary, you will look up the word fence and you will see
a wooden structure
The dictionary definition omits the word "is".
There's no passive voice here. "Made" is an adjective, formed from the past participle.
Let's look at the passive voice.
I made this birthday cake.
This birthday cake was made by me.
That last sentence uses the passive voice.