请多多指教The question being discussed is of great importance.

Question

The question being discussed is of great importance. is是系动词，of great importance.of怎么可以连接great importance做表语呢？我是第一次看到这样的句型，请知道给小弟解释下，请多多指教。

Answer 1

一、“be of+抽象名词”，这时的of短语相当于这个名词的同根形容词，作为表语表示主语的性质或特征。of的意思是“具有、具备”等，常用于该结构的名词常见的有
of use=useful；of nouse=useless；of importance=important等。如：
The matter is of great importance.=The matter is very important.
在形容词前常用very来修饰，在“of+抽象名词”结构中，名词前常用great, much等来修饰。再如It is of great importance for college students to master a foreign language.
=It is very important...对大学生来说，掌握一门外语是很重要的。

二、“be of+集合名词或其它类型的名词”，相当于belong to或have。of表示归属关系或“有”的意思。如：The army and the people are of one family.
=The army and the people belong to one family.军民是一家。

三、“be of+物质名词”表示主语是“用某种材料构成或制作的”，相当于be made of或be built of。如：Our building was of bricks.=Our building was built of bricks.
我们的楼房是砖建的。

四、be of+(表示种类、颜色、年龄、形状、价格等）名词，多用来表示主语的特征。这类结构的主语可以是人，也可以是物，其中的of可以省略。常用于该结构的名词有：kind,age,colour,size,height,shape,type,way,price等。如：
Several of the stamps were of the unusual kind.其中几张邮票是不同种类的。
The two boys are of the same age.这两个男孩年龄相同。
She is of a different way of thinking.她的思维方式与众不同。
These two kinds of article are of the same price.这两种物品价格相同。

五、“be of+名词”也可以表示“来源、组成”。如：
He was of a poor peasant family.他出身贫农家庭。
The committee is of seven people.该委员会由7人组成。

六、“be of+形容词的最高级”相当于one of...。如：
Mr.Wang is of the best teachers in our school.
=Mr Wang is one of the best teachers in our school.
王老师是我们学校里最好的老师之一。

Answer 2

是系动词，of great importance.of怎么可以连接great importance做表语呢？我是第一次看到这样的句型，
其实这是很常见的结构：抽象名词当表语时，要在这个抽象名词前加of，即：be of +抽象名词，等于这个抽象名词的形容词：be + 形容词。如：
Character is of great importance. 人品最为重要。=Character is very important.
The book is of great use.=The book is very useful.
His idea is of great value.=His idea is very valuable.
还有类似的词：help=helpful