There is a case for using short words in writing. It's simpler to write, faster to comprehend, and makes your writing more succinct. Here's a list of common words you can replace next time:
Purchase > Buy
Humorous > Funny
Possess > Have
Appears > Seems
Transpire > Occur, Happen
Signify > Mean
Reference > Refer to
Individual > Person
Subsequently > Later
Speak > Talk
Lengthy > Long
Utilize > Use
Demonstrate > Show
Retain > Keep
Approximately > About
Require > Need
Remain > Stay
Regarding > About
Reside > Live
Principal > Main
Frequently, Oftentimes > Often
Currently > Now
Obtain > Get
Perhaps > Maybe
Amongst, Amidst, Whilst > Among, Amid, While
Does that mean we forever ban these words from our writing? No. If you find yourself repeating a certain word, then it's okay to use alternatives to switch up the sentence.
Other scenario where you'd prefer the long version is in formal writing. You do not want to come across as being too casual in formal setting.
Lastly, you can use the long word when there's distinction in meaning between the two words.
For example, you wouldn't say:
I want to demonstrate you a ring.
instead you would write:
I want to show you a ring.