An academic piece of writing should have an academic formal register (style). A formal register is designed to place a distance between the writer and the reader.
I/you/we/they/he/she
The general rule is to avoid using first person in academic writing. It is encouraged to use formal language.
For example:
Instead of ‘they say’, ‘I will explain x’, or ‘you can see x’ you could write ‘it is claimed that’, ‘x will be explained’, or ‘x can be seen’.
Contractions
Avoid using contractions (short forms) e.g. ‘it’s’, ‘don’t’, ‘won’t’, hasn’t’, or ‘can’t’. Instead, use the long form as it is generally considered to be more formal e.g. ‘it is’, ‘does not’, ‘will not’, ‘has not’, or ‘cannot’.
Slang
Avoid using colloquial words and expressions or vague terms, such as ‘stuff’
‘like’, ‘about’, or ‘basically’.
sort of/kind of → reasonably, relatively, rather, somewhat
lots of/a lot of → a number of, numerous, a significant/considerable number of
really/very → highly, extremely, exceptionally
like → such as
Use linking words to help your writing sound more scholarly. Linking words will also help you to maintain flow and establish clear relationships between ideas.
Avoid using ‘and’, ‘so’ or ‘but’ at the beginning of sentences, and try to avoid using ‘etc.’ and ‘like’ (to exemplify).
Phrasal verbs (multi-word verbs) are less common in academic writing. For example, instead of using the terms ‘take out’ and ‘put in’, the writer might use ‘extract’ and ‘insert’.
look into → investigate
break out → start
come over → approach
carry on → continue
cut down → reduce
look at → observe