What is another word for fully grown?
Pronunciation: [fˈʊli ɡɹˈə͡ʊn] (IPA) 
Fully grown is a common phrase used to describe a living thing that has reached its full physical size and maturity. However, there are many synonyms that could be used instead of fully grown, depending on the context. For people, terms like adult, mature or fully developed could be used instead. For animals, synonyms could be fully formed, fully developed, or fully matured. Plants can be described as fully-bloomed or fully-matured, while objects or materials which have reached their full size and maturity can be described as fully formed, fully developed or fully-developed. Regardless of the context, there are always alternatives to using the phrase "fully grown" which can add variety and interest to your writing.
