effectual

/ɪˈfɛktʃuəl/

Effectual means good at achieving the results you want. The most effectual method for avoiding cavities? Brush, floss, lay off the candy, and see your dentist every 6 months.

Wait, aren't effectual and effective basically the same adjectives with the same meaning? Well, generally speaking, yes. But if you want to get really nit-picky, you might note that effectual actually describes something that produces the desired result, but in a big way. Effective simply gets the job done. No one is going to call you out for using either word interchangeably though, as long as it's done effectually.

Definitions of effectual

1. adjective

   producing or capable of producing an intended result or having a striking effect
   “his complaint proved to be effectual in bringing action”

   synonyms: effective, efficacious

   hard-hitting, trenchant

   characterized by or full of force and vigor

   impelling

   markedly effective as if by emotional pressure

   impressive, telling

   producing a strong effect

   rough-and-ready

   crude but effective for the purpose at hand

   efficacious

   marked by qualities giving the power to produce an intended effect

   efficient

   being effective without wasting time or effort or expense

   potent, stiff, strong

   having a strong physiological or chemical effect

   impactful, powerful

   having great power or force or potency or effect

   useful, utile

   being of use or service
2. adjective

   having legal efficacy or force
   synonyms: legal, sound

   valid

   well grounded in logic or truth or having legal force