1 (wiktionary) 2 (vi.wikipedia) 3 (en.wikipedia) 4 (glosbe)
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COMPOUNDS
bất lực 
incapable, incompetent, ineffective, impotent, powerless, helpless; impotence
có hiệu lực to be valid, effective, take effect, come into effect, be in force
có hiệu lực ngay lập tức to be effective immediately
có hiệu quả to be effective, show results
có kết quả effective; to benefit from, get something out of
công hiệu efficient, effective; efficiency, effectiveness
diệu kế very effective trick
hiệu lực validity, effectiveness
hiệu nghiệm effective, efficient
hiệu quả effect, result; effective; efficient
hữu hiệu efficient, effective, valid
không hiệu quả ineffective
không linh ineffective, doesn’t work
kiến hiệu effective, efficacious
linh effective
linh dược effective drug, marvelous drug
quân số effectives, strength
thần hiệu marvelous efficacy, very effective, very efficacious
tề gia nội trợ run a household (effectively)
vô hiệu ineffective, ineffectual, without effect
vô hiệu lực to be ineffective, inefficient, void
vô tích sự ineffective, good-for-nothing
yếu hèn weak, feeble, cowardly, spineless, ineffective, incapable, weak-kneed, weak-willed
đạt kết quả to obtain results, be effective
bất lực incapable, incompetent, ineffective, impotent, powerless, helpless; impotence có hiệu lực to be valid, effective, take effect, come into effect, be in force có hiệu lực ngay lập tức to be effective immediately có hiệu quả to be effective, show results có kết quả effective; to benefit from, get something out of công hiệu efficient, effective; efficiency, effectiveness diệu kế very effective trick hiệu lực validity, effectiveness hiệu nghiệm effective, efficient hiệu quả effect, result; effective; efficient hữu hiệu efficient, effective, valid không hiệu quả ineffective không linh ineffective, doesn’t work kiến hiệu effective, efficacious linh effective linh dược effective drug, marvelous drug quân số effectives, strength thần hiệu marvelous efficacy, very effective, very efficacious tề gia nội trợ run a household (effectively) vô hiệu ineffective, ineffectual, without effect vô hiệu lực to be ineffective, inefficient, void vô tích sự ineffective, good-for-nothing yếu hèn weak, feeble, cowardly, spineless, ineffective, incapable, weak-kneed, weak-willed đạt kết quả to obtain results, be effective