-and Caml, which are prominent *functional programming languages*. We'll explain
-what that means during the course.
-
-* **Scheme** is one of two major dialects of *Lisp*, which is a large family
-of programming languages. The other dialect is called "CommonLisp." Scheme
-is the more clean and minimalistic dialect, and is what's mostly used in
+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 a truth-value), 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 (generating 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 effects). Programming languages like C and Python and JavaScript and so on are predominantly of this sort.
+
+In truth, nothing that gets marketed as a "programming language" is really completely 100% functional/declarative, and even the
+languages I called "imperatival" will have some "functional" *fragments* (they evaluate `1+2` to `3`, also). So these labels aren't
+strictly exclusive. The labels are better thought of as concerning different
+*styles* or *idioms* of programming. 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. Languages like Python and JavaScript are sometimes themselves
+described as "more functional" than other languages, like C.
+
+
+In any case, here is some more context for the three languages we will be focusing on.
+
+* **Scheme** is one of two or three major dialects of *Lisp*, which is a large family
+of programming languages. Scheme
+is the more clean and minimalist dialect of Lisp, and is what's mostly used in