Modifiers matching endeavor:

• healthy,
• economic,
• creative,
• artistic,
• worldly,
• humanitarian,
• future,
• aesthetic,
• humanistic,
• scholarly,
• philanthropic,
• mental,
• athletic,
• everyday,
• professional,
• female,
• aquatic,
• important,
• over,
• cooperative,
• individual,
• heterogeneous,
• productive,
• spiritual,
• cultural,
• legal,
• intellectual,
• animal,
• technological,
• commercial,
• profitable,
• competitive,
• voluntary,
• meaningful,
• sporting,
• simple,
• dangerous,
• wonderful,
• out,
• defined,
• active,
• feminine,
• beneficial,
• dynamic,
• real,
• usual,
• lucrative,
• noncompetitive,
• common,
• complex,
• illicit,
• strategic,
• agricultural,
• positive,
• physical,
• maritime,
• diverse,
• conventional,
• basic,
• vocational,
• marine,
• scientific,
• unique,
• new,
• organisational,
• traditional,
• imaginative,
• technical,
• outdoor,
• personal,
• actual,
• secular,
• serious,
• unrelated,
• joint,
• private,
• medical,
• fundamental,
• musical,
• outside,
• academic,
• multinational,
• supporting,
• strenuous,
• entrepreneurial,
• surgical,
• industrial,
• literary,
• annual,
• challenging,
• organized,
• cerebral,
• stimulating,
• expensive,
• moral,
• practical,
• exciting,
• educational,
• modern,
• amateur,
• local,
• current,
• complicated,

Simple categories matching challenging:

• location,
• domain,
• structure,
• activity,
• exercise,
• site,
• works,
• surface,
• application,
• behavior,
• work,
• condition,
• topic,
• area,
• place,
• thing,
• industry,
• event,
• behaviour,
• occupation,
• movement,
• game,
• toy,
• space,
• task,
• endeavor,
• issue,
• situation,
• system,
• sport,
• content,
• project,
• pursuit,
• illness,
• discipline,
• sector,
• environment,