Specifically, I'm interested in concepts and conceptual development from the view of linguistic semantics and language acquisition. Ray Jackendoff talks about the relation between conceptual and semantic structure quite a bit. His definition of 'concept' seems to be a mental representation that can serve as the meaning of a linguistic expression. This seems to work for nouns (e.g. 'dog' denotes the concept DOG), but what are we to make of verbs? What about temporal forms? Does the English past-tense marker, '-ed,' express the concept PAST? What about modal forms? Does the English epistemic modal auxiliary 'might' express the concept POSSIBILITY?