Open English Wordnet
Adjectives
(s)thoughtful, serious-mindedcharacterized by solemn, sincere manner“a sensible young man”, “The serious-minded doctor carefully considered what to do next.”
(a)heedful, attentive, thoughtful, paying attentiontaking heed; giving close and thoughtful attention“heedful of the warnings”, “so heedful a writer”, “heedful of what they were doing”