中堅【ちゅうけん】
nucleus, backbone, mainstay, key figure, medium-level, mid-level, middle-ranking, midsize, main body (of troops), crack troops, select troops, center field, centre field, center fielder, centre fielder, athlete competing in the middle-number match in a team competition, i.e. second in 3-on-3, third in 5-on-5 (kendo, judo, etc.)
堅実【けんじつ】
steady, sound, stable, safe (e.g. business), reliable, trustworthy, solid
堅固【けんご】
solid, strong, firm
堅持【けんじ】
holding on to, sticking to
堅調【けんちょう】
firm (market), bullish, strong (sales, economy, etc.), steady, sound
手堅い【てがたい】
sound, sure, safe, secure, trustworthy, reliable, solid, steady, firm
堅守【けんしゅ】
strong defense, strong defence
堅気【かたぎ】
honest, respectable, decent, respectable occupation (i.e. not yakuza, prostitute, etc.), person in a respectable occupation
底堅い【そこがたい】
stable (market) after having bottomed out
堅苦しい【かたくるしい】
formal, strict, ceremonious, stiff