Focus is key to understanding processes of syntactic and prosodic readjustments in the Romance languages. Since, prosodically, it must be the most prominent constituent in the sentence, focus associates with the nuclear pitch accent, which may be shifted from its default rightmost position when the syntactic position of the focus also changes. The application of specific syntactic operations depends both on the size and on the subtype of focus, although not always unambiguously. Subject inversion characterizes focus structures where the domain of focus covers either the whole sentence (broad-focus) or a single constituent (narrow-focus). Presentational constructions distinctively mark broad focus, avoiding potential ambiguity with an SVO structure where the predicate is the focus and the subject is interpreted as topic. In narrow-focus structures, the focus constituent typically occurs sentence-final (postverbal focalization), but it may also be fronted (focus fronting), depending on the specific interpretation associated with the focus.
Semantically, focus indicates the presence of alternatives, and the different interpretations arise from the way the set of alternatives is pragmatically exploited, giving rise to a contextually open set (information focus), to contrast or correction (contrastive or corrective focus), or to surprise or unexpectedness (mirative focus). Whether a subtype of focus may undergo fronting in a Romance language is subject to variation. In most varieties it is indeed possible with contrastive or corrective focus, but it has been shown that focus fronting is also acceptable with noncontrastive focus in several languages, especially with mirative focus.
Finally, certain focus-sensitive operators or particles directly interact with the narrow-focus constituent of the sentence and their association with focus has semantic effects on the interpretation of the sentence.