- adequate to accomplish a purpose; producing the intended or expected result: effective teaching methods; effective steps toward peace.
- actually in operation or in force; functioning: The law becomes effective at midnight.
- producing a deep or vivid impression; striking: an effective photograph.
- prepared and available for service, especially military service.
- a member of the armed forces fit for duty or active service.
- the effective total of a military force.
- productive of or capable of producing a result
- in effect; operativeeffective from midnight
- producing a striking impression; impressivean effective entrance
- (prenominal) actual rather than theoretical; realthe effective income after deductions
- (of a military force, etc) equipped and prepared for action
- physics (of an alternating quantity) having a value that is the square root of the mean of the squares of the magnitude measured at each instant over a defined period of time, usually one cycleSee also root mean square
- a serviceman who is equipped and prepared for action
late 14c., from French effectif, from Latin effectivus “productive, effective,” from effect-, stem of efficere (see effect (n.)). Effectively in the sense of “actually” is attested by 1650s. Related: Effectivity.