Improvisação vs. improviso
While both improvisação and improviso translate to "improvisation", they function differently in a sentence. Improvisação generally acts as a noun describing the process, technique, or act of improvising over a period. Improviso often implies the state of being unprepared, the specific result of the act, or is used in the common adverbial phrase "de improviso" (impromptu/off the cuff).
Improvisação
B2This word refers to the action, method, or faculty of improvising. It is commonly used when discussing the skill in arts (like jazz or theater) or the act of creating a temporary solution to a problem.
A improvisação é uma parte essencial do teatro moderno.
(Improvisation is an essential part of modern theater.)
O mecânico fez uma improvisação criativa para consertar o carro.
(The mechanic did a creative improvisation to fix the car.)
A banda é conhecida pela sua capacidade de improvisação no palco.
(The band is known for its capacity for improvisation on stage.)
Este curso ensina técnicas de improvisação para falar em público.
(This course teaches improvisation techniques for public speaking.)
Improviso
B2This refers to the result of the action, a specific impromptu creation (like a verse or musical solo), or the quality of being sudden. It is most frequently used in the phrase "de improviso", meaning something was done on the spur of the moment.
Ela teve que fazer um discurso de improviso durante o jantar.
(She had to make an impromptu speech during dinner.)
O poeta recitou um lindo improviso para a plateia.
(The poet recited a beautiful improvisation for the audience.)
Foi tudo feito de improviso, sem nenhum planejamento anterior.
(It was all done off the cuff, without any prior planning.)
Eu não gosto de lidar com o improviso em reuniões de negócios.
(I do not like dealing with the unforeseen elements in business meetings.)
Summary
Use improvisação when discussing the technique, process, or the act itself (e.g., "a class on improvisation"). Use improviso when referring to a specific unexpected instance, a poetic creation, or when using the phrase "de improviso" to describe something done without preparation.