guitar chord
F♯5
F♯1C♯5
Root and fifth, no third at all — neither major nor minor, which is the point.
Written the other way round it is G♭5 — the same twelve keys on a piano, a different piece of notation.
What is true of it
F♯5 is F♯ and C♯ — 1 and 5 counted from F♯.
No fingering of F♯5 fits a hand on the guitar: inside four frets, with the strings that sound next to each other and the root underneath, there is nothing to hold.
Where its notes are on the neck
The brass dots are F♯, the root. Everything else is a chord tone with its degree printed in it.
With a different note underneath
F♯5/C♯
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An inversion is the same chord with a different note lowest. The name changes to a slash name because the bass is what a listener hears as the foundation.