Literally: On TV recently, I heard a reporter say that someone had literally hit rock bottom. There were no cliffs involved. Or teenagers who have literally died of embarrassment because their moms said something stupid like "hello" in the wrong tone or drove a car whose windows were held in place by screwdrivers. They literally do not know that they mean the opposite: figuratively.
Quantum: In quantum mechanics, the word refers to the increments of energy that an electron may have. Electrons have energy values that increase like going up the stairs versus going up a ramp. These increments are usually very small but somehow the word has morphed into popular usage implying a huge increase as in the expression: quantum leap. I understand that most people were spared the rigors of Physical Chemistry but when one works for a company that specializes in the products of research, one would hope* that the powers that be had some inkling of the correct meaning of the word. In a mission statement once, it was stated that we would not be satisfied with incremental increases in scientific knowledge but only in quantum increases i. e. breakthroughs. Well easier said than done and so very wrong on so many levels.
*I used this particular wording in honor of the now deceased photographer who was appalled with my often misuse of the word hopefully as in hopefully this reaction will work. Above is the correct usage. He was much more pedantic than I but occasionally I would win. He once was proud that a particular compound was found to be very analytical as its found values perfectly matched its calculated values. I rightly pointed out a compound is either analytical or it isn't. The fact that the numbers fit exactly in the range was coincidental. This is how some scientists spend their time.
Organic: I would tell visiting groups that I was an organic chemist and immediately visions of bean sprouts came to their minds. Nothing, for the most part, I did was 'natural'. I made compounds that are not to be found in nature. A few times I would start with a 'natural product' such as citronellol, found in citronella, because it had the correct configuration with its substituents but by the time I was finished, one would not recognize the original structure.
Penultimate: Recently in a written eulogy of my former coworker, there was something said about his penultimate goal in life with the meaning that this goal somehow was vastly elevated over 'ultimate'. In chemistry, the penultimate product is just one step before the final product: the desired. In common usage, 'y' is the penultimate letter: no more, no less.
Hoi polloi: I have misused this to mean the elite when it really refers to the common people.
Positive/negative: Testing positive for cancer is certainly negative
Could eat no fat
could eat no lean..
Can people who are opposites in so many ways get along? We'll see.