Synonyms and related words :
aboriginal, acute, basal, basic, central, charged, clamorous, climacteric, compelling, critical, crying, deciding, decisive, desperate, dire, elemental, elementary, embryonic, emergent, essential, exigent, fundamental, generative, genetic, germinal, high-pressure, high-priority, imperative, imperious, important, in embryo, in ovo, insistent, instant, kairotic, loaded, major, momentous, necessary, original, pivotal, pregnant, pressing, primal, primary, primeval, primitive, primordial, pristine, protogenic, radical, rudimentary, seminal, urgent, vital