well-grounded

[ wel-groun-did ]

/ ˈwɛlˈgraʊn dɪd /

based on good reasons; well-founded: His opposition to the scheme is well-grounded.

well or thoroughly instructed in the basic principles of a subject: She is well-grounded in mathematics.

Origin of well-grounded

Middle English word dating back to 1325–75

There are a lot of remarkable things to explain, instead of hyping up a fear which is not well-grounded.

Sanjay Gupta, on the Ebola Front Lines |Tim Teeman |August 4, 2014 |DAILY BEAST
They are highly intelligent, well-grounded parents with strong values.

Organizing for Action Wants Your Newtown Anniversary Party to Be a Success |Stuart Stevens |December 12, 2013 |DAILY BEAST
He himself looked forward to the event without fear, and with a wise and well-grounded hope.

Great Men and Famous Women. Vol. 2 of 8 |Various
Also there is a well-grounded belief that McGraw has subsidized the scoreboard boy so that he cheats the visitors somewhat.

Practical English Composition: Book II. |Edwin L. Miller

These considerations, though profoundly wise, did not convince me, because I thought his inference was not well-grounded.

The Memoirs of Cardinal de Retz, Complete |Jean Francois Paul de Gondi, Cardinal de Retz
He was keenly alive to Garrett's every action, resulting from what he believed to be well-grounded suspicions.

'As Gold in the Furnace' |John E. Copus
But in the course of negotiations with them he learned a piece of news which caused him well-grounded anxiety.

A Short History of the Royal Navy 1217 to 1688 |David Hannay

well-grounded

well instructed in the basic elements of a subject

another term for well-founded