The italicized words here are different from the other lexical categories that we have seen so
far. They introduce a complement clause, marked above by the square brackets, and may be
sensitive to the tense of that clause. A tensed clause is known as a ‘finite’ clause, as opposed to
an infinitive. For example, that and if introduce or combine with a tensed sentence (present or
past tense), whereas for requires an infinitival clause marked with to. We cannot disturb these
relationships: