For all intensive purposes
If you're using this phrase to mean "for all practical purposes," then for all intents and purposes, you're doing it wrong (see what we did there?). The phrase, "for all intensive purposes" is a mondegreen, which is defined as a misheard version of a phrase, saying or slogan. The phrase you're actually looking for (as you've probably guessed by now) is "for all intents and purposes." Try these fancy words if you want to sound smarter.
A doggy dog world
What you meant to say was "dog eat dog world," right? If so, it's understandable that you misheard/reshaped it as "doggy dog world." This type of error is known as an "eggcorn," which reshapes an established word or phrase phonetically, without changing the actual meaning of the phrase (just as "eggcorn" reshapes the word "acorn" without changing its actual meaning). Learn about the 15 words that have completely changed meaning.
All and all
We hope that what you meant to say was "all in all," which is an idiom (a word or phrase whose meaning can't be understood outside its cultural context) meaning "everything being taken into account." If you actually meant "all and all," then you're just being redundant. Please never do this when it comes to acronyms, or grammar snobs will be saying you have RAS (repetitive acronym syndrome. But if you're looking to be concise, you might want to consider replacing "all in all" with "in sum." Here are 20 words even smart people mispronounce.
Day in age
In this day and age, you should really know better than to say "day in age." It's an eggcorn, which means we know you meant well. But now you know better. Avoid these 10 words that will immediately make you sound old.
Butt naked
The thing about being butt naked, is that it's more than just your butt that's hanging out there making you look foolish. The actual term is "buck naked," although truth be told, so many people have misheard it and misstated it as "butt naked" that grammarians actually are beginning to accept "butt naked" as a proper idiom. Here are 10 words that people say aren't words but are!
All for not
If you think this grammar exercise is all for not, then you might want to reconsider—because nothing is actually "all for not," whereas something that is pointless may, indeed, be "all for naught." Yeah, it's old-timey. But it's the right way to say it. Sorry, not sorry. By the way, dictionary editors say this is the most misused word in the English language.
A whole nother
What's a "nother"? Exactly. There's no such thing. It's a whole nother story may sound cute and colloquial, but it certainly isn't grammatical. What is grammatical is "a whole different story" or "another story" or even "a whole other story." Choose one, and sound like a boss.
At nauseum
You know when someone's droning on and on and on about something to the point where you feel like you're going to be sick? Well, they're going on ad nauseam. It's Latin for "to sickness." We know the "ad" sounds an awful lot like "at," but we can assure you it's not. And if we go on ad infinitum (to infinity) about it, you'll forgive us, won't you? Here are 19 words you never realized were the same backwards and forwards
Excetera
This one gets pronounced incorrectly more than it gets spelled incorrectly, simply because in writing, it tends to end up abbreviated as "etc." But it's pronounced "Et-CEH-Terrah." There is no "x" to be found anywhere. Now that we've got you thinking about abbreviations, wouldn't you love to know what "Ms" really means?
Safety deposit box
The phrase referring to a box in which valuables are stored is "safe-deposit box" because it's a box in which you can make a safe deposit. Not a safety deposit. But this eggcorn is highly understandable because when you say "safe-deposit box" aloud, the first two syllables run together to sound exactly like "safety." Don't miss these 33 middle school vocabulary words adults get wrong.