一張一弛[icchouisshi] tension and relaxation
弛む[yurumu] to become loose
弛み[tarumi] slack
弛む[tarumu] to slacken
中弛み[nakadarumi] a slump

弛緩[shikan] relaxation (e.g. of muscles)
弛張振動[shichoushindou] relaxation oscillation
筋弛緩剤[kinshikanzai] muscle-relaxant drug
弛まない[tayumanai] untiring
腕弛るい[kattarui] listless

隈無く[kumanaku] all over
然り気無い[sarigenai] nonchalant
だらし無い[darashinai] slovenly
途轍も無い[totetsumonai] extravagant
とんでも無い[tondemonai] unthinkable

無け無し[nakenashi] very small amount which looks like nothing
無駄にする[mudanisuru] to render futile
悪虐無道[akugyakubudou] treacherous
意気地無し[ikujinashi] coward
一も二も無く[ichimonimonaku] unhesitatingly