I came across this sentence on a Britannica page:
The titles of Jakobson’s works indicate the expanding scope of his research
Why is expanding used here instead of expansive? Is expanding a commonly used adjective? Any difference from expansive?
Expansive means the scope of his research is already large, while expanding means the scope of his research is still continuing to grow larger.
Expansive means "very large", while expanding means "becoming progressively larger".
If the scope of Jakobson's work is expansive, then we'd expect the titles of his works to cover many different subjects - that is, the scope is very large.
If the scope of Jakobson's work is expanding, then we'd expect later titles to cover more subject areas than the earlier ones do - that is, the scope gets larger over time.
Looking up expanding on Wiktionary we see:
The page for Glossary: participle says:
A form of a verb that may function as an adjective or noun. English has two types of participles: the present participle and the past participle. In other languages, also future, perfect, future perfect participles.
So, to answer the question title, all participles, including expanding, may act as adjectives.
expanding means it's still growing (present participle). The main meaning of expansive is "comprehensive".