Sometimes, parentheses can be vital to your essay (except when they're not). I think they're more properly used when they contain either a subjunctive clause, or an adjective. Anything else is like intentionally breaking fluidity -- and that's the job of an n-dash.

There are very few cases in which parentheses are actually necessary to your work. The easiest example to cite when they are relevant is in technical writing (see Appendix A). It can also be used, still in technical writing, to set up an acronym which you will use later. Saying Theory of Constraints (TOC) now will save you time and space when you have to say TOC later.

I use it to clarify something that doesn't really deserve its own sentence, but you can't use n-dashes for because you already are using the n-dash somewhere else in the same paragraph. For example:

"As compared with current policy, adopting a new machine reduces expected costs to PhP 4,290.71 (0.14% lower than simply changing policies), saving management PhP 143,152.56 over 365 days – a 1.6% increase compared to changing policies but not buying the new machine."

Parentheses also feel like n-dashes that take less time mentally to pronounce. So, it feels like things in parentheses are less important than if you put them in the dashes.

"Still resting from yesterday, I suddenly found out I had an exam today (I thought it was tomorrow), so I went ahead and crammed."

Versus

"Still resting from yesterday, I suddenly found out I had an exam today -- I thought it was tomorrow -- so I went ahead and crammed."

Of course, this is just my (incomplete) list, and again, you can use the parentheses with adjectives that feel more secondary to the sentence. The fact that you can omit the things in the parentheses automatically make us think that they're already secondary, and less important. That's why, when reading sentences aloud that have something enclosed in parentheses in them, we often skip the things said in the parentheses. It might be easy to take these things for granted (and we often do), but they are quite important -- especially if you're a writer.

(Sorry if this reply's use of parentheses seems forced. There's just too many parentheses!)

Sometimes, parentheses can be vital to your essay (except when they're not). I think they're more properly used when they contain either a subjunctive clause, or an adjective. Anything else is like intentionally breaking fluidity — and that's the job of a dash.

There are very few cases in which parentheses are actually necessary to your work. The easiest example to cite when they are relevant is in technical writing (see Appendix A). It can also be used, still in technical writing, to set up an acronym which you will use later. Saying Theory of Constraints (TOC) now will save you time and space when you have to say TOC later.

I use it to clarify something that doesn't really deserve its own sentence, but you can't use em dashes for because you already are using the dash somewhere else in the same paragraph. For example:

"As compared with current policy, adopting a new machine reduces expected costs to PhP 4,290.71 (0.14% lower than simply changing policies), saving management PhP 143,152.56 over 365 days — a 1.6% increase compared to changing policies but not buying the new machine."

Parentheses also feel like dashes that take less time mentally to pronounce. So, it feels like things in parentheses are less important than if you put them in the dashes.

"Still resting from yesterday, I suddenly found out I had an exam today (I thought it was tomorrow), so I went ahead and crammed."

Versus

"Still resting from yesterday, I suddenly found out I had an exam today — I thought it was tomorrow — so I went ahead and crammed."

Of course, this is just my (incomplete) list, and again, you can use the parentheses with adjectives that feel more secondary to the sentence. The fact that you can omit the things in the parentheses automatically make us think that they're already secondary, and less important. That's why, when reading sentences aloud that have something enclosed in parentheses in them, we often skip the things said in the parentheses. It might be easy to take these things for granted (and we often do), but they are quite important — especially if you're a writer.

(Sorry if this reply's use of parentheses seems forced. There's just too many parentheses!)