Same same but different - parallel construction

Parallel construction is writing ideas or phrases in the same grammatical structure to show they’re connected. It’s the writing equivalent of dressing twin toddlers in the same outfit so people know they’re twins and say “Awww, twins!“. PC — let's call it PC, my fingers are too lazy to type it out every time — helps people process your writing (or your twins) faster.

We'll get into some of the more sophisticated varieties of PC later on but the most common one is lists. This is where it's easy to F up your PC.

A list isn't just this week's groceries scribbled on an envelope. In writing, a list is also called a series, a catalogue, or an inventory. That was a list. When you write a list, the sentence structure implies that all the items in the list are structurally alike, equally important, and related to each other in some way. There, I did it again!

Not parallel: When I get home from work, I like having a spoonful of dry Milo, falling into bed, and to watch reels until my brain has reset.
Parallel: When I get home from work, I like having a spoonful of dry Milo, falling into bed, and watching reels until my brain has reset.

In the not parallel example, “to watch reels” is a different tense and therefore a different grammatical structure than its brethren “having a spoonful of Milo” and “falling into bed”.

This is an easy enough concept when your list is simple, like this one:

Not parallel: Live, love, farting.
Parallel: Live, love, fart.

It can get a bit complicated when you start writing long lists full of phrases, like this one:

Not parallel but pretty cool: My hobbies include eating raisins, birds, and to tell people I am the inventor of the hot dog.
Parallel, still cool: My hobbies include eating raisins, birdwatching, and telling people I am the inventor of the hot dog.

As always, break this rule if you feel like it but only if you can explain the rule you're breaking.

TL;DR? Items in a list must be structurally similar to be grammatically correct. This is called parallel construction.