Sweaters are often made of wool.是什么意思？

Sweaters are often made of wool.

毛衣常由羊毛织成。

sweaters

n. 毛衣( sweater的名词复数 )；

例句
I was wearing two sweaters under the green army jacket...
我在绿军装里套了两件毛线衫。

are

vi. （用于第二人称单复数现在时，第一、三人称复数现在时）是；n. 公亩（等于100平方米）；

例句
We are scared to abandon ourselves to our feelings in case we seem weak or out of control.
我们不敢放纵自己的情感，以免显得太过软弱或缺乏自制。

often

adv. 常常，经常，时常，再三；

例句
Genetic abnormalities are more often associated with faults in paternal DNA than in maternal DNA.
相对于母本DNA,基因畸变往往更多地与父本DNA上的缺陷相关。

made

adj. …制的，（人工）做成的，拼成的，虚构的，保证成功的；v. 使(make的过去式和过去分词)；

例句
Single people are treated as an aberration and made to pay a supplement.
独身者被当成异类，而且要付一笔额外的费用。

of

prep. 关于，属于…的，由…制成；aux. 助动词 [非标准用语、方言] =have [主用于虚拟语气]；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

wool

n. 羊毛，羊毛制品，（幼虫的）毛，羊毛覆盖物；

例句
A long thin wool coat and a purple headscarf protected her against the wind...
一件薄薄的羊毛长外套和一条紫色的头巾为她挡了风。