This course aims at discussing the challenges that modification poses for linguistic theory, with a particular attention to the semantics of modification. We will focus on issues related to the compositionality and ontology of modifiers of various categories and we will discuss the semantic properties of different kinds of adjectives and adverbs. We will then pay particular attention to degree and manner modification, entertaining a cross-categorial analogy between degrees and manners. Particular questions we will address include the following. Are degrees and manners semantic primitives in our ontology, or are they more complex or derivable from other notions (e.g. the notion of event and state kinds or tropes)? Is degree modification in the adjectival domain the same as degree modification in the verbal and nominal domains? Similarly, are there cases of manner modifiers in the nominal and adjectival domains?