+and OCaml. Occasionally we will also make remarks about Haskell. All three of these
+are prominent *functional programming languages*. The term "functional" here means they have
+a special concern with functions, not just that they aren't broken. But what precisely is
+meant by "functional" is somewhat fuzzy and even its various precisifications take some
+time to explain. We'll get clearer on this during the course. Another term used roughly the same as "functional"
+is "declarative." At a first pass, "functional" or "declarative" programming is primarily focused on complex
+expressions that get computationally evaluated to some (usually simpler) result. In class I gave the examples
+of `1+2` (which gets evaluated in arithmetic to 3), `1+2 < 5` (which gets evaluated in arithmetic to 'true), and `1`
+(which gets evaluated in arithmetic to 1). Also Google search strings, which get evaluated by Google servers to a
+list of links.
+
+The dominant contrasting class of programming languages (the great majority of what's used
+in industry) are called "imperatival" languages, meaning they have more to do with following a sequence of commands (what we
+called in class "side-effects", though sometimes what they're *alongside* is not that interesting, and all the focus is instead
+on the effect). Programming languages like C and Python and JavaScript and so on are all of this sort.
+
+In fact, nothing that gets marketed as a "programming language" is really completely 100% functional/declarative, and even the
+imperatival languages will have purely functional fragments (they evaluate `1+2` to 3, also). So these labels are really
+more about *styles* or *idioms* of programming, and languages like Scheme and OCaml and especially Haskell get called "functional languages" because
+of the extent to which they emphasize, and are designed around those idioms. Even languages like Python and JavaScript are sometimes
+described as "more functional" than some other languages. The language C is about as non-functional as you can get.