Overly informal language
In academic writing, essays, etc., you should avoid using words associated with informal writing or informal speech. There is very often a more formal word that is more appropriate to the genre.
Things would be different if Sweden were a bigger country.
Things would be different if Sweden were a larger country.
The immigrants had a lot of trouble learning the language.
The immigrants had great difficulty learning the language.
A lot of the information in the report is wrong.
A great deal of the information in the report is false.
I guess I’ll apply again next year.
I suppose I will apply again next year.