On Tue, 29 Jan 2019 at 11:36, Stewart Fraser <[log in to unmask]> wrote:
> What do you mean by expletive subjects and thematic subjects ?

An expletive is a word that has no semantic meaning, and only serves a
syntactic role. The most classic example I know of is the "It" in
"It's raining." -- what is raining? Nothing. Raining just happens. The
"It" has no referent, it's just there to satisfy a syntactic
requirement of English grammar.

> Also I am a bit hazy about the term pro-drop.

Basically, it means that the language allows you to leave out ("drop")
pronouns (or, equivalently, noun phrases) when they can be inferred
from context.