decided, decidedly, decisive, decisively

When referring to things, decided means unquestionable; and when referring to people, it means free from doubt, and thus resolute or determined.

• That plan is a decided mistake, and I am sure Clarence will regret it.
• Susannah is a very decided person and almost always gets what she wants.

In contrast, decisive refers to quick, efficient decision making and to people capable of making such decisions.

• Elena is a decisive shopper who always succeeds in making excellent purchases in just a few moments.

Decisive also conveys the idea that something is conclusive, as in a decisive advantage, a decisive event or moment, or a decisive victory.

• The Battle of Midway was a decisive victory for the Allies; it turned the tide of the Pacific War.

In general, decidedly is a synonym for undoubtedly or definitely.

• That is decidedly the best wine I have tasted all year!

Decisively is an equivalent for resolutely.

• The lone forward ran decisively toward his target, ignoring the crowd’s jeers and his teammates’ cries.