A conclusion is a final part or summing up of something. A denouement is a final resolution or tidying up of the intricacies of a plot, as in a drama or novel, often a tragedy. The literary application of denouement sets it apart from the much more general term conclusion. However, denouement is also used to refer to outcomes or resolutions of a series of occurrences that may read like a novel or drama, but take place—however regrettably—in real life.
The key idea behind the word innocuous is safety. An innocuous home remedy, for instance, is safe and poses no danger of exacerbating whatever needs remedying in the first place. Innocuous is also used to mean inoffensive, as in the case of a remark that will be universally well received. On the flip side, sometimes this word suggests a little too much safety and not enough zest: innocuous is sometimes used to describe things that are not interesting, stimulating, or significant.
Something that is silly is absurd, ridiculous, or irrational—but not always in a negative way. Sometimes the word silly suggests amusement or even endearment (you silly goose!). Frivolous, on the other hand, almost always suggests a lack of value, merit, or necessity. A frivolous person is someone who is self-indulgently carefree and does not engage seriously with matters. A frivolous lawsuit is one that lacks legal merit and is not to be taken seriously.