English normally expresses an indirect or a reported statment by a that clause (she said that it was true), but can also use an infinitive (she declared it to be true) or participle (she regarded it as being true). Latin always and only uses the infinitive method.
There is no seperate word for 'that'.
The subject of the infinitive is accusative. This must alwayss be expressed. If it is the same as the introductory verb, a reflexive pronoun must be used.
The tense of the infinitive is that of what was said or thought at the time (in the actual or…