The "conditional zero" is used
when the time referred to is
now or always and the
situation is real and possible.
This type of book is usually
used to talk about general
facts. The tense of both
propositions is the "simple
present". In conditional type 0
sentences, the term "if" can
usually be replaced by "when"
without changing the meaning.
first conditional
The "type 1 conditional" is
used to refer to the
present or future when
the situation is real.
Conditional type 1 refers
to a possible condition and
its probable outcome. In
these sentences, the "if"
clause adopts the "simple
present" and the main
proposition the "simple
future".
third conditional
The "type 3 conditional" is
used to refer to a time in the
past and a situation contrary
to reality. It is based on facts
that are opposed to what is
being expressed. The
conditional type 3 is used to
refer to a past condition that
is not real, as well as to its
probable outcome in the past.
In these sentences, the clause
"if" adopts the "past perfect"
and the main proposition the
"perfect conditional".
second conditional
The "type 2 conditional"
is used to refer to a
time that can be now or
at any time and to a
situation that is not real.
These prayers do not
allude to facts. The
conditional type 2 is
used to refer to a
hypothetical condition
and its probable
outcome. In these
sentences, the "if"
proposition adopts the
"simple past" and the
main clause the "present
conditional".