effective

US /əˈfek.tɪv/

UK /əˈfek.tɪv/

1.

successful in producing a desired or intended result

:

•

The new policy proved to be very effective in reducing crime.

•

This medicine is highly effective against the flu.

:

efficacious successful productive potent powerful

:

ineffective useless

2.

(of a law or agreement) coming into operation or effect

:

•

The new regulations will be effective from January 1st.

•

The contract is effective immediately.

:

operative valid binding in force

:

ineffective invalid

:

effect effectively effectiveness in effect to no effect to that effect greenhouse effect