What is another word for long established?
Pronunciation: [lˈɒŋ ɪstˈablɪʃt] (IPA) 
The phrase "long established" can be changed with a variety of synonyms to add more depth and interest to written and spoken English. Some alternatives include "well-established," "time-honored," "venerable," "traditional," "deep-rooted," "settled," "ancient," "historic," "enduring," and "firmly entrenched." Each of these terms carries a slightly different nuance and connotation but share the general idea of something that has been in existence for a significant amount of time and is thus considered reliable, respected, or deeply rooted in a particular community or culture. Choosing the right synonym can make a piece of writing or speech more vibrant while also conveying the intended message effectively.
