(Je vais essayer d'utiliser mon horrible français ici.)une forêt épaisse
une forêt dense
l'herbe pousse dru (adverb here)
une averse drue
il a les cheveux drus
une végétation touffue/ épaisse
une population dense
une circulation dense
exactly... alas.Thank you CarolineR
I take it then there is no "rule" which would determine whether to use "Dru" versus using "épais".
I guess that would be too easy...
So it's just a matter of reading or hearing enough useage of the 2 different adverbs/adjectives over time, as you so kindly help me to see with your list of useages.