This particular word is something of a distraction. We are mostly familiar with it in one form or another (more apparent if you remove the suffix "-to"). "Emuna" means faith, and it is included in the various formulations of Maimonides and others, such as "ani ma'amin be'emuna sh'leima...," "I believe with a perfect faith..." Far more usual is the exclamation "amen," which affirms the statement or prayer of a public presenter.
But whether in Hebrew or English, being able to say the meaning does not necessarily mean understanding it. After all, what is faith? To suggest that it is the affirmation of something otherwise without evidence is to reduce it to an irrational opinion. And when we use "faith" to describe the varieties of religious experiences, we are really talking about religion – the practices and beliefs that are organized around communities.
Faith actually has more to do with stocks and securities than with religion. At its root in Hebrew, it means something that is a reliable investment, something dependable, a surety. Emuna is a bond – the financial kind, not the shared-experience kind. It is an iron-clad promise.
When we use the affirmation "amen" at the end of a blessing or prayer, we are declaring that the words are true and certain. We acknowledge their accuracy and bind ourselves to what they explicitly state and implicitly infer. That meaning enables a listener to gain the ritual benefit of hearing another pronounce a blessing yet merit the recitation himself or herself – "amen" in that sense means "and that goes for me, too."
Just to complicate things a little bit, the word in the Amidah also carries that little suffix I conveniently jettisoned. "Emunato" means "his faith." The "his" in this context is God – God establishes, sustains and fulfills God's own faith, not ours, as an expression of the divine power. And in what or with what does God have this deep bond? Well, that's next.