There's a Wikipedia article here about the word "faith" in Christianity; which begins,
The word "faith", translated from the Greek πιστις (pi'stis), was primarily used in the New Testament with the Greek perfect tense and translates as a noun-verb hybrid; which is not adequately conveyed by the English noun.
An explanation of what the Greek perfect tense is can be found here:
Perfect Tense
The basic thought of the perfect tense is that the progress of an action has been completed and the results of the action are continuing on, in full effect. In other words, the progress of the action has reached its culmination and the finished results are now in existence. Unlike the English perfect, which indicates a completed past action, the Greek perfect tense indicates the continuation and present state of a completed past action.
For example, Galatians 2:20 should be translated "I am in a present state of having been crucified with Christ," indicating that not only was I crucified with Christ in the past, but I am existing now in that present condition.
"...having been rooted and grounded in love," Eph 3:17
Sentences which summarize it include,
The pi'stis-group words in the New Testament can thus be interpreted as relating to ideas of faithfulness, fidelity, loyalty, commitment, trust, belief, and proof. The most appropriate interpretation and translation of pi'stis-group words in the New Testament is a matter of recent controversy, particularly over the meaning of pi'stis when it is directed towards Jesus.[4]
Do the words have nuances that have been lost in the translation to the simple English word faith?
Based on the Wikipedia article, perhaps it implies a personal connection, the "fidelity" of human relationships: "Jesus is/was my friend", and "do this is remembrance of me", that kind of thing.
I won't try to say what the same word was used to mean, in the Old Testament.
The use of the "perfect" tense (meaning 'completed', not meaning 'without fault') is appropriate for referring to actions which have been completed (e.g. Jesus's life, death, and resurrection; a Christian's past baptism causing their present salvation; etc.): see also the notion of Christianity as "good news".
Per Wikipedia (here and here), the Buddhist word "faith" also (i.e. perhaps similarly to the Christian word) includes the meanings of "trust" and "loyalty".
The descriptions given in this article seem to me to imply that the words have the following in common:
- Hear that something exists (dharma or law)
- Trust in the spiritual attainment of the teacher (Buddha or Christ)
- Practice/study/discovery of what the message really means
- Happiness, confidence, satisfaction if/when/because one is able to align one's life with one's faith