adverb
just like; exactly like; as if
Adverbial use, often followed by a form of ようだ (e.g., さながら…のようだ). Describes a strong resemblance or vivid similarity.
その光景はさながら夢のようだった。
The scene was just like a dream.
彼の演技はさながら本物の侍のようだ。
His performance is exactly like a real samurai.
suffix
just like ...; virtually like ...; as if it were ...
Suffix-like use after a noun, often with ～に or ～の. Creates a simile meaning 'just like N' or 'as if it were N'.
その庭園はさながら絵画のようだ。
The garden is just like a painting.
彼女はさながら女王のように振る舞った。
She behaved as if she were a queen.
まるで is a more common and colloquial adverb meaning 'as if' or 'completely', often used with ようだ. さながら is more literary and emphasizes vivid resemblance.
あたかも is a formal/literary adverb meaning 'as if' or 'just like', similar to さながら but used in more abstract comparisons. さながら often implies a concrete, visual likeness.
The origin is uncertain. It may be a compound of 然 (sa, 'so') + ながら (nagara, 'while/as'), but the exact derivation is unclear.