monos

In its predicative and attributive uses, μόνος describes a person, thing, or group as either physically unaccompanied or as being the sole representative of its kind. These two shades, isolation and exclusivity, are facets of one idea: the absence of any other beside the subject.

The isolation sense pictures someone left without company: Jesus withdrawing to pray alone, the disciples left behind, a grain of wheat lying alone in the ground. The exclusivity sense makes a bolder claim: not merely that no one else is present, but that no one else could take the same place. This is the theological weight of "the only true God" (John 17:3) and the doxologies that address God as "the only God" (1 Timothy 1:17; Jude 1:25). There, μόνος is not about solitude but about incomparability, God alone holds immortality, God alone is holy.

The two shades shade into each other at the margins, and the NT authors seem to feel that tension: "I am not alone," Jesus says (John 8:16), meaning both that he is not isolated (the Father is with him) and that he is not acting as a lone, uncorroborated witness: both senses reinforce the claim.

The neuter singular form μόνον is regularly used as an adverb, meaning "only" or "merely", restricting the scope of the verb or clause it modifies. This use is frequent in the NT, appearing in commands ("only believe," Mark 5:36; Luke 8:50), comparisons ("not only... but also," a staple of Pauline argument), and limiting qualifiers ("only by faith," "only the word," "not merely in word").

As an adverb, μόνον does not describe isolation or exclusivity of a subject; it narrows what is true or permissible about an action. The distinction from the adjective use is semantic, not just grammatical: "Jesus alone" (adjective, no one else was there) is a different claim from "only believe" (adverb, the one thing required is faith). English Bibles tend to blur this because "only" and "alone" overlap in English, but the Greek forms make the distinction clear.