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.