42.306

it is hard when it is firm or solid

it is hard when it is real

when it is significant or considerable

when it is appreciable or substantial

it is hard to ignore when it is notable

it is hard to conquer when it is severe

grave or complicated

when it is highly problematic

42.307

the material is hard when it is rigid

rigid and inflexible

muscle stiffness

stiff neck

42.308

the problem is hard when it is serious

serious and complex

when it is intricate

intricate relationship

intricate network of

intricate design

it is hard to receive or obtain when it is profound

profound effect

profound impact

profound knowledge

42.309

when something is hard it requires much effort

it can be arduous

it can be laborious

especially when that something you want to change is resistant

resistant to change

when it is unalterable

when it is resilient

unalterable or implacable

42.310

to procure something that is hard one needs to be relentless

relentless pursuit

relentless pursuit

relentless or even ruthless

ruthless exploitation

when the material is invariable it is durable

it resists impacts

it resists impacts

durable goods

durable equipment