Just by belief or by faithfulness?

From the brief study, "Three Biblical keywords: What do language sciences clarify?"

... Here we examine facts of Ancient Greek (AG) relevant not only to several foundational hypotheses of Dixon’s “basic linguistic theory”—universal word classes, universal clause structure, universal transitivity typology, etc.—but also to the comprehension and translation of central parts of humanity’s most widely read text, the Christian Bible (recorded firstly in AG manuscripts). Central to the Christian Bible are ideas expressed with a set of related words—pistos, pistis, pisteuō—translated most often into modern English with “faithful”, “faith”, “to believe”, respectively, yet revealed in dictionary entries to be far more difficult to understand, at least for lexicographers (LSJ, s.v.; BDAG, s.v.). For example, pisteuō is understood to have the senses of “to comply” (LSJ, s.v. 2) and “to entrust” (LSJ, s.v. II; BDAG, s.v. 2) in some ancient texts. (Continued....)