The straightforward adjective informed describes someone or something that has or is prepared with information or knowledge. An informed decision, for instance, is one that is made with relevant information taken into account. The adjective savvy is not so transparent. Someone who is savvy about something is experienced or knowledgable on that topic—you’re not going to get much by them (not that you should try!). Where informed emphasizes the presence of information, savvy emphasizes practical understanding and a familiarity that lends itself to shrewd maneuvering or strategic decision making. Now go forth, friends, and relish your synonym-savvy status!
Brace yourselves, synonym seekers, because today's word pair takes us into iffy territory. The adjectives doubtful and dubious both deal with a lack of certainty. Doubtful is commonly used to describe things that are unlikely or improbable, e.g. It is doubtful that the event will take place without an audience. Dubious emphasizes suspicion, especially with regard to the quality or propriety of something. A dubious claim is one that should not be taken at face value. An action or argument that is described as morally dubious is perhaps not as high-minded or noble as it seems.
The adjectives proper and decorous are strong synonyms, but proper has many more meanings. Consider the difference between a proper (suitable) time to plant strawberries and proper (accurate) punctuation—this is just the tip of the semantic iceberg when it comes to what proper can convey. The adjective decorous is far less common and deals exclusively with what is considered socially acceptable or in good taste. Decorous is defined as “characterized by dignified propriety in conduct, manners, appearance, or character,” and it emphasizes a careful respectfulness, as in one’s behavior or language.