On this International Cat Day, we look at a distinction of the utmost importance, the difference between dozing and sleeping. To sleep is to be in a state of deep rest in which consciousness is suspended (the viral video of a kitten sleeping flat on its back), or to regularly enter this state for an extended period (She sleeps in the spare room.). Doze implies being lightly asleep (I'm not asleep; I was just dozing. Cats hear everything while they doze.), or slipping in and out of a light sleep (doze in front of the television on Sunday afternoon). When we unintentionally fall into a light sleep, we often say we dozed off, and when we're surprised or confused about having been asleep, we say, “I must have dozed off!”

Empty and vacant denote absence of content or contents. Empty means without the appropriate or usual contents: an empty refrigerator; empty bottles. An empty room could be a bare room or one without people in it (the theater was almost empty). Vacant is usually applied to that which is temporarily unoccupied: a vacant position; three vacant apartments. A vacant lot is a piece of property which has no buildings on it and lies unused.

Combine and synthesize refer to mixing or joining together two or more things into one. Combine has the broader range of usage, and is looser with respect to how closely associated the joined elements become. Recipes instruct us to combine the diced onions, peppers, and spices in a bowl. Combine also applies to more abstract things: a major that allows her to combine her love of history with biology. Synthesize implies a transformative joining together. In science, it refers to the manufacture of a new substance by means of a chemical reaction between different elements (cells synthesize and secrete insulin). Outside of science, synthesize is mostly used for the mental work of bringing together a number of ideas, information, evidence, or data, in order to make sense of them as a whole (a paper synthesizing existing research). Similarly, a musician might synthesize styles from various musical traditions to create a new work.