Our main objective is to derive the decay rate for the semileptonic decays D→Vℓ+νℓ(ℓ=e,μ), where V represents a vector particle. In these decays, the vector particle V decays into three pseudoscalar particles. To accomplish this, we evaluate the phase-space factor for the five-body decay with a set of eight independent variables which uniquely define a point in the phase space. We further conduct a detailed investigation of the D→ωℓ+νℓ, where ω subsequently decays into π+π−π0, within the Standard Model and in a general effective field theory description of the weak interactions at low energies. The outcomes of this study have potential applications in the measurement of D→ω form factors. These measurements can be performed using data obtained from BESIII. Published by the American Physical Society 2024