if;
unless;
lest;
provided that;
if it is the case;
in this sense;
once...;
if possible;
if necessary;
if so;
if not all;
if anything.
归纳总结类:
in other words;
on the whole;
in sum;
therefore;
hence;
in short;
in brief;
to sum up;
in conclusion;
in summary;
to conclude;
the conclusion can be drawn that...;
for this reason;
in short.