句子的一致性：指句子结构完整，时态、语态，语气及句式的一致，举重个部分共同表达一个独立、完整的思想。句子各成分之间的关系应协调，连贯，自然平稳。
下面来看一下句子不统一的几种情况：
1）句子意思表达不完整
× The lecture was given in such an interersting way.
√ The lecture was given in such an inereresting way that everyone enjoyed it very much.
2）句子的主从关系模糊
× We are going to visit John, and he is our English friend.
√ We are going to visit John who is our English friend.
3) 连接词使用不当
× The main reason he was absent was because he was ill.
√ The main reason he was absent was that he was ill.
4) 主谓不一致
× Every teacher and student were invited to go to the party.
√ Every teacher and student was invited to go to the party.
5) 中心不明白
× I was watching a film last night, I suddenly found Mary sitting in front of me.
√ When I was watching a film last night, I suddenly found Mary sitting in front of me.