1. Pluperfect, both the tense, and the word, which sounds like a particularly ripe fruit with sweet and juicy indigo flesh.
2. The Elusive Semicolon; often, we forget about this powerful object; frequently, we use him incorrectly.
3. Particularly clever adjectival phrases. That was an example of a dependent adverbial clause.
4. Conjunctive Adverbs. A little known fact is that the disease known as ‘pinkeye’ (or, conjunctivitis) is actually caused by that squinty thing that happens when one experiences boring old “ending in -ly” adverbs too much.
5. Tiny little parts of speech. Articles like “a”, “an”, and “the”; Pronouns like “it”.