silly
adj.adj. showing a lack of serious thought or good judgment. You use this to describe something funny, childish, or a bit foolish.
adj. lacking in seriousness, prudence, or common sense. Often used to describe behaviour that is playfully lighthearted or trivial rather than genuinely harmful.
Don't be silly, of course you can come with us.
The children spent the entire afternoon making silly faces at each other in the mirror.
While the proposal was dismissed by the board as a silly distraction, it actually contained the seeds of a very effective marketing strategy.
From Middle English seely, sēlī, from Old English sǣliġ, ġesǣliġ (“lucky, fortunate”), from Proto-West Germanic sālīg, from sāli; equivalent to seel (“happiness, bliss”) + -y. Doublet of Seelie. The semantic evolution is “lucky” to “innocent” to “naive” to “foolish”. Compare the similar evolution of daft (originally meaning “accommodating”), and almost the reverse with nice (originally meaning “ignorant”).
A gradable adjective that can take comparative and superlative forms (sillier, silliest).