Talk:didn't

Inflection, not contraction

While ~n't looks like a contraction, it's actually an inflection, similar to ~ed or ~ing. Contractions share the following properties:

1. Will add on to a wide variety of word categories (e.g., verb, prepositions, adjectives, etc.)
2. Don't have seemingly arbitrary word that they will not attach to.
3. Don't change the pronunciation of the preceding word.
4. Don't change the syntax of the sentence.

You'll find that ~n't fails all of the above tests. For more, see the paper by Zwicky & Pullum here.