Modifiers matching difficulty:

• mental,
• mechanical,
• maternal,
• psychological,
• emotional,
• severe,
• physical,
• interpersonal,
• neurological,
• surgical,
• personal,
• natural,
• visual,
• local,
• serious,
• subjective,
• behavioural,
• clinical,
• experienced,
• habitual,
• minor,
• spiritual,
• sexual,
• psychiatric,
• respiratory,
• invisible,
• real,
• unanticipated,
• practical,
• traditional,
• secondary,
• internal,
• environmental,
• domestic,
• financial,
• unexpected,
• sensory,
• nutritional,
• academic,
• particular,
• economic,
• special,
• stressful,
• leaning,
• stable,
• typical,
• educational,
• basic,
• extraneous,
• conceptual,
• reproductive,
• mathematical,
• important,
• hormonal,
• somatic,
• major,
• parental,
• developmental,
• extra,
• everyday,
• chronic,
• administrative,
• unforeseen,
• home,
• behavioral,
• motor,
• unusual,
• concurrent,
• social,
• past,
• persistent,
• extreme,
• legal,
• prevalent,
• smaller,
• commercial,
• periodic,
• external,
• possible,
• related,
• anatomical,
• common,
• logistical,
• structural,
• progressive,
• significant,
• technical,
• cognitive,
• linguistic,
• single,
• computational,
• temporary,
• operational,
• underlying,
• technological,
• experimental,
• perceptual,
• neuropsychiatric,
• functional,
• acute,
• ongoing,
• regulation,

Simple categories matching behavioural:

• trait,
• variable,
• change,
• factor,
• action,
• disturbance,
• process,
• marker,
• condition,
• component,
• event,
• disorder,
• characteristic,
• disease,
• state,
• drive,
• training,
• problem,
• standard,
• competence,
• adaptation,
• measure,
• dimension,
• study,
• information,
• quality,
• pattern,
• test,
• precept,
• signal,
• technique,
• analysis,
• disposition,
• science,
• scientist,
• attribute,
• means,
• cause,
• difficulty,
• unit,
• discipline,
• distinction,
• style,
• barrier,
• rule,
• treatment,
• strength,
• therapy,
• setting,
• tendency,
• sign,
• adjustment,
• procedure,
• feature,
• interaction,
• domain,
• noise,
• tie,
• impact,
• property,
• difference,
• strategy,
• activity,
• skill,
• asymmetry,
• relationship,
• response,
• abnormality,
• act,