string theory
physical theory of quantized one-dimensional objects with conformal symmetry, which can describe gravitation, gauge theory and other phenomena
string field theory
a theory of strings in a second-quantized formalism on the target space (as opposed to the first-quantized formalism on the worldsheet)
F-theory
formalism for describing nonperturbative compactifications of Type IIB string theory via Calabi–Yau manifolds admitting elliptic fibrations
superstring theory
theory of strings with supersymmetry