Correct

改 vs 改变

/ gǎi vs gǎibiàn /
Strokes

Definition

改 as a Verb, and 改变 as a Verb and Noun, which means [change; alter; alteration].

Example

As a verb, 改 and 改变 both mean "to change, in either concrete or abstract way".
1) 改 is more colloquial and mostly used with monosyllabic words, while 改变 with disyllabic words. But this is not absolute.

2) In the two examples above, 改变 cannot be used in example ①, but 改 can be used instead in example ②. That indicates that 改 is relatively free in collocation.
1
yuánlái
原来
jiào
xiǎomíng
李小明
  
,
hòulái
后来
gǎi
le
míng
  
,
jiào
yǒng
李勇
  

His former name is Li Xiaoming,and later he changed his name to Li Yong.

2
Yuán
dìng
de
huà
计划
jīng
已经
gǎi
  
(
gǎibiàn
改变
  
)
le
  

The original plan has been changed.

改变 are mostly artificial, that is, to make sth. different from before, usually better than before.
3
Zhège
这个
chéngshì
城市
gǎibiàn
改变
le
miànmào
面貌
  

The city has changed.

4
men
我们
yào
gǎibiàn
改变
gōngzuò
工作
fāng
方法
  

We should improve our work methods.

改 also means "to correct (mostly applied to writings)"; while 改变 cannot.
5
Lǎoshī
老师
gěi
gǎi
zuòwén
作文
  

The teacher corrected my writing.

6
Zhè
shǒu
shī
yǒu
liǎng
gōu
可以
gǎigǎi
改改
  

You can make a change in the two lines of the poem.

改 has the meaning of making right; while 改变 cannot.
7
zhè
máobìng
毛病
de
gǎi
gǎi
  

You should correct the habit.

8
jīng
已经
gǎi
hǎo
le
  
,
hái
kǎoshàng
考上
le
xué
大学
  

He has turned to be a good boy, and he is at college now.

改变 as a noun mostly functions as the object of 有, 随着.
9
Zhège
这个
guīhuà
规划
yǒu
diǎnr  
一点儿
gǎibiàn
改变
  

The plan has been made a little change.

10
Suīzhe
随着
qíng
情绪
de
gǎibiàn
改变
  
,
biéren
别人
shuōhuà
说话
de
语气
suí
随和
duō
le
  

With his mood changing, he is more easygoing when talking to others.