Academic writing uses formal language rather than informal or colloquial language (spoken or informal language). Informal language is much more widely used, thus part of developing an academic writing style is simply being aware of when we are using informal language.
The following basic principles are helpful:
Contracted forms should be avoided
Words are normally written out in academic English.
Example: use cannot instead of can’t
Example: use it is instead of it’s
Colloquial language , i.e. spoken and informal language should be avoided
Example: The results of the study were really surprising.
Academic style: The results of the study were very surprising.
Very is used since really is informal and colloquial.
Example: The data collection methods were good and the preliminary results are promising.
Example: The data collection methods were effective and the preliminary results are promising.
Language and punctuation indicating your attitude should be avoided
Example: Researchers found that 95% of registered university students plan to vote in the upcoming election!
Academic style: Surprisingly, researchers found that 95% of registered university students plan to vote in the upcoming election.
Source: The key points above are from Appendix 4 in the Cambridge Academic English Advanced Students’ Book by Martin Hewings and Craig Thaine, Cambridge University Press 2012.