模糊限制语（Hedging language）用于表达确定性或不确定性的口吻。在学术写作中，作者可能对其研究领域中的某些主张不够确信，或观点合理但证据不够充分。因此，使用谨慎或不确定的语言（即模糊限制语）是常见的做法。
动词 appear 和 seem 可用于表达不确定性。它们可与存在句（动词 to be 结构）连用，以体现谨慎态度。
There appears to be a correlation between social class and likelihood of getting to university.
It seems to be the case that non-native speakers of English rely more on the mother tongue. （非英语母语者似乎更依赖母语。）
appear 和 seem 还可与从属连词 as if/though 连用：
- appears as if/though + 从句
It appears as if/though they had been working together.
- seems as if/though + 从句
It seems as if/though expeditions to Mars will be possible in the future.
此外，appear 和 seem 可与 that + 从句 结构连用：
- It seems that the scope of the native speaker in Korea is narrow...
作者也可通过引用动词（reporting verbs）表达对主张的不确定性：
- Other studies suggest that using L1 supports language acquisition.
- Larsen-Freeman and Long (1991) argue that input alone is not enough.
（Larsen-Freeman 和 Long（1991）认为，仅靠输入是不够的。）
- Liu et al. (2004) claim that students may drop out early.
（刘等人（2004）声称，部分学生可能提前退学。）
通过不确定性情态动词（may/might, could, can）可实现模糊限制：
- Advocacy groups may ask institutions to support their stance.
（倡导团体可能会请求法官、政客或科学家支持其立场。）
- A policy image might fit one venue better.
- Nuclear power could help reduce dependence on oil.
- Actors can use evidence to legitimize their stance.
- It is clear/apparent that...
- It may be perceived that...
- It has been suggested/argued/claimed that...
- It seems evident that...
- Teachers probably spoke more English than usual.
- Strategies do not necessarily involve only institutions.
- Issues could potentially get onto the agenda.
- Research appears to indicate that social class affects participation.
- Reports seem to suggest that a US-Iran deal may be signed.
- It appears that interviews may not be possible for all.
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