Recall that the subjunctive forms are strongly associated with subordinate clauses, one sentence embedded into another.
A sentence embedded into another sentence can act as the subject:
· SOMETHING is typical.
· THAT WE EAT IN THE CAFETERIA is typical.
· SOMETHING sounds interesting.
· THAT YOU ARE VISITING THE MUSEUM doesn't sound interesting.
Note that, in English, if the embedded sentence is the subject, we usually move it to the end, and we have to insert a 'filler' subject in front:
· (IT) is typical THAT WE EAT IN THE CAFETERIA.
· (IT) doesn't sound interesting THAT YOU ARE VISITING THE MUSEUM.
In this kind of sentence in Spanish, the subjunctive way is usually used in the subordinate clause, in other words, in the embedded sentence:
· ALGO es típico.
· QUE COMAMOS EN LA CAFETERÍA es típico. (not "comemos")
· ALGO no suena interesante.
· QUE UDS. VISITEN EL MUSEO no suena interesante. (not "visitan")
This is a very subtle change in the verb form, and most native Spanish speakers do it without even realizing it.
The most common linking verbs are: es/está (is), suena (sounds), parece (appears/looks/seems).
In sentences like these, the basic exceptions are explicit affirmations of truth, certainty, undeniability, and clarity/obviousness:
· ALGO es cierto.
· QUE COMEMOS EN LA CAFETERÍA es cierto. (not "comamos")
Using the actual adjective that asserts truth, certainty, etc. is the key. An assertion may be true, certain, undeniable, etc., and still require the subjunctive:
· Es cierto QUE LOS CUBANOS HABLAN ESPAÑOL.
· Es normal QUE LOS CUBANOS HABLEN ESPAÑOL.
This list of basic exceptions is relatively short, and of course there are more, but not many: cierto, verdadero, correcto, seguro, claro, obvio, evidente, patente (evident, clear), visible, perceptible, real, innegable (undeniable), indiscutible, incuestionable, indudable, inequívoco.
Note that "verdadero" is the adjective "true", and "(la) verdad" is the corresponding noun "(the) truth". They both affirm truth and both require the indicative.
The word "seguro" can mean "sure/definite" and also "safe". If it means "sure/definite", the subordinate clause should use the indicative (since it is an explicit affirmation of truth). But if it means "safe", the subordinate clause should use the subjunctive.
The word "correcto" can mean "correct = true" and also "correct = appropriate". If it expresses "true", the subordinate clause should use the indicative (since it is an explicit affirmation of truth). But if it expresses "appropriate", the subordinate clause should use the subjunctive.
Negation of the truth, certainty, etc., requires the subjunctive:
· ALGO no es evidente.
· QUE TÚ COMPRENDAS no es evidente. (not "comprendes")
Watch out for negative expressions that affirm truth, such as "no es falso" and "no es negable" (negatable = deniable), which affirm truth and certainty. These are actually logical, but also tricky: