A tenor guitar is a fretted, four stringed instrument, most commonly shaped like a guitar.
scale length (approx):
23" (Gibson tenors are 22 3/4")
(6 string guitar = 25.5", plectrum guitar = 26")
standard string gauges:
.036 .024 .016 .010
(use bronze strings for acoustic, steel for electric)
Octave mandolin tuning: GDAE
"Guitar" tuning: DGBE
other possible tunings:
"Guitar" tuning, transposed up a fourth
(uke tuning, but G is 1 octave lower): GCEA
Slide: CGCG, or DADA
Instruction manuals and chord books for the tenor guitar are hard to come by, so beginners should find books for the tenor banjo, which is tuned in the same way.