Parallel structure requires items in a list to be parallel in tense and form. For example, a sentence cannot state "They loved going to the park where they went running, jumped, and laughed" but rather "They loved going to the park where they ran, jumped, and laughed."
So now we're talking parallel structure and parallel structure is just what it sounds like. It's when you have items in a list, whether they're items or adjectives or verbs, whatever they are, they have to be parallel which means the same in tense and in form. So take a look at this. This is this example of a sentence that's in parallel structure. "They loved going to the park where they ran, jumped and laughed." So the three things in the list are ran, jumped and laughed. They're all past tense verbs, so they're all in the same form. You'd want this, rather than this. "They loved going to the park where they went running, jumped and laughed." because in this sentence you've got two verbs in past tense, but then you have this verb running in the gerund tense. So you really want to make sure you pay close attention to the fact that you want your verbs or your items in the same structure, alright. So, here's the trick with parallel structure. When you're looking to fix it, I know I always tend to hit kind of a dead end with it and I end up getting really frustrated, I've got a paper that's marked parallel structure. What I always have to remind myself is that there is always more than one way to make something parallel. So I intend to look at it from one way and then when I get super frustrated, take a step back and think well, if I can't change that, then what else can I change? So let's take a look at this example sentence. On the first read through, what I want to do is I just want to go through and mark the items in the list and decide what format they are in then we'll go back and try to fix it. So it says, "Sometimes I think going back to school would be a really great opportunity for making more friends, to get a chance to be more focused on my studies and I would want to try to be more involved than I actually was." So we've got three ideas there in the list. The first one is, "It would be a great opportunity for making more friends," Alright. The second is, "It would be a great opportunity to get a chance to be more focused on my studies," and then the third is, "I would want to try to be more involved than I actually was." Those are three hugely different forms here. Here we've got an '-ing' verb, here we've got a verb in the infinitive and then here we've got an actual complete sentence. So we've got to go through and make this a little bit more parallel. So I start going through and it makes sense here I see my infinitive and I know that I can easily change this first one to an infinitive. So I could say, "It would be a really great opportunity to make more friends, to get a chance to be more focused," and I've got two of my things kind of in order. Now let's look at here and see how we can make "I would want to try to be more involved than I actually was," to our infinitive form. And we already have to try here so I can make this parallel by just getting rid of "I would want to," and now I've got the sentence, "Sometimes I think going back to school would be a really great opportunity to make more friends, to get a chance to be more focused on my studies and to try and be more involved than I actually was." So we took that really unparallel sentence and just by identifying the types of phrases that we had, and then matching them up, we're able to make it parallel.