In ordinary usage, “accurate” and “precise” are often used as rough synonyms, but scientists like to distinguish between them. Someone could say that a snake is over a meter long and be accurate (the snake really does exceed one meter in length), but that is not a precise measurement. To be precise, the measurement would have to be more exact: the snake is 1.23 meters long. The same distinction applies in scientific contexts to the related words “accuracy” and “precision.”
A breakup is what happens when two people break up. The one-word form is the result, whereas the two-word form is the action that leads to it.
When paying someone a compliment like “I love what you’ve done with the kitchen!” you’re being complimentary. A free bonus item is also a complimentary gift. But items or people that go well with each other are complementary.
In geometry, complementary angles add up to 90°, whereas supplementary ones add up to 180°.
“Everyone” means “everybody” and is used when you want to refer to all the people in a group: “Everyone in my family likes spaghetti carbonara.”
But if you’re referring to the individuals who make up a group, then the phrase is “every one.” Examples: “God bless us, every one” (may each individual in the group be blessed). “We wish each and every one of you a Merry Christmas” (every single one of you). In the phrase “each and every one” you should never substitute “everyone”).
In normal usage, a handicap is a drawback you can easily remedy, but a disability is much worse: you’re just unable to do something. But many people with disabilities and those who work with them strongly prefer “disability” to “handicap,” which they consider an insulting term. Their argument is that a disability can be compensated for by—for instance— a wheelchair, so that the disabled person is not handicapped. Only the person truly unable by any means to accomplish tasks because of a disability is handicapped. The fact that this goes directly counter to ordinary English usage may help to explain why the general public has been slow to adopt it; but if you want to avoid offending anyone, you’re safer using “disability” than “handicap.”
Many of the people involved also resent being called “disabled people”; they prefer “people with disabilities.”
“If” is used frequently in casual speech and writing where some others would prefer “whether”: “I wonder if you would be willing to dress up as a giant turnip for the parade?” Revise to “I wonder whether. . . .” “If” can’t really be called an error, but when you are discussing two alternative possibilities, “whether” sounds more polished. (The two possibilities in this example are: 1) you would be willing or 2) you wouldn’t. In sentences using “whether” “or not” is often understood.) Don’t substitute the very different word “whither,” which means “where.”
“Maybe” is an adverb meaning “perhaps,” so if you are uncertain whether to use this word or the phrase “may be,” try substituting “perhaps”: “Maybe she forgot I said I’d meet her at six o’clock” becomes “Perhaps she forgot. . . .” When the substitution makes sense, go with one word: “maybe.” When you are wondering whether you may be waiting in the wrong cafe, you’re dealing with a verb and its auxiliary: “may be.” Two words.
A psychologist is a person who has studied the mind and earned a Ph.D. or Psy.D. Although some definitions state that psychologists have undergone clinical training but cannot prescribe medicines, there are research psychologists who are not engaged in clinical work at all, but merely do experiments to discover how our minds work. Some of their work can concern animal rather than human minds.
A psychiatrist is technically an M.D. specializing in the treatment of mental problems who can prescribe medicines. They are licensed medical doctors, and get irritated when they are called “psychologists” and when psychologists are called “psychiatrists.”
Psychotherapist is not a technical term, and may be used by anyone claiming to offer therapy for mental problems. That someone is called a “psychotherapist” tells you nothing about his or her qualifications. But qualified clinical psychologists and psychiatrists can be properly called “psychotherapists.”
A psychoanalyst is a very specific kind of psychotherapist: a licensed practitioner of the methods of Sigmund Freud.
You say “Hello, Mr. Chips” to the teacher, and then tell him about what you did last summer. You can’t “tell that” except in expressions like “go tell that to your old girlfriend.”
I must confess that I do not myself observe the distinction between “that” and “which.” Furthermore, there is little evidence that this distinction is or has ever been regularly made in past centuries by careful writers of English. However, a small but impassioned group of authorities has urged the distinction; so here is the information you will need to pacify them.
If you are defining something by distinguishing it from a larger class of which it is a member, use “that”: “I chose the lettuce that had the fewest wilted leaves.” When the general class is not being limited or defined in some way, then “which” is appropriate: “He made an iceberg Caesar salad, which didn’t taste quite right.” Note that “which” is normally preceded by a comma, but “that” is not.