allthingslinguistic:

swampwyvern:

your fave is problematic: adjectives

• cannot be characterized in terms of a prototype
• not a semantically definable class of concepts
• lexicalize properties or characteristics that are indeterminate or variable in terms of time stability

No but seriously there are entire academic papers about how problematic adjectives are. (I also strongly endorse the book that this quote is from, Describing Morphosyntax.)