冠词指的是定冠词the ,不定冠词an和a，the，an，a可以放在名词前，或者一些固定短语中，例如
on the tree
an unusual day
a university
指示代词有四个this(这个)
that（那个） these（这些 ）those（那些）指示代词构成的句子是
this /that +a/an+单数名词
This is an apple.
That is your book.
Those/These +are+复数名词。
These are teachers.
Thoese are beautiful flowers.
