Lifeblood

Noun

 * 1) The blood needed for continued life; that blood which if lost causes death.
 * 2)  That which is required for continued existence or function.
 * Gasoline is the lifeblood of the modern city.

Thesaurus
Rh factor, Rh-negative, Rh-positive, Rh-type, Rhesus factor, anima, animating force, antibody, antigen, arterial blood, atman, bathmism, beating heart, biological clock, biorhythm, blood, blood bank, blood cell, blood count, blood donor, blood donor center, blood group, blood grouping, blood picture, blood platelet, blood pressure, blood serum, blood substitute, bloodmobile, bloodstream, breath, breath of life, circulation, clinical dextran, dextran, divine breath, divine spark, elan vital, erythrocyte, essence of life, force of life, globulin, gore, growth force, grume, heart, heartbeat, heartblood, hematics, hematologist, hematology, hematoscope, hematoscopy, hemocyte, hemoglobin, hemometer, humor, ichor, impulse of life, inspiriting force, isoantibody, jiva, jivatma, leukocyte, life breath, life cycle, life essence, life force, life principle, life process, living force, neutrophil, opsonin, phagocyte, plasma, plasma substitute, pneuma, prana, red corpuscle, seat of life, serum, soul, spark of life, spirit, type O, venous blood, vis vitae, vis vitalis, vital energy, vital flame, vital fluid, vital force, vital principle, vital spark, vital spirit, white corpuscle

Translations

 * French: élément moteur, forces vives, élément vital