The concept of neutrino oscillations is revisited. Using the Quantum Field Theory approach and applying plane waves for the initial and final states, the processes of neutrino production, propagation, and detection are described through a single Feynman diagram. The updated S-matrix approach ensures energy and momentum are conserved during neutrino oscillations. A master formula is provided to calculate the rate of charged lepton production for neutrinos oscillating over a macroscopic distance $L$. The process $\pi^{+} + n \to \mu^{+} + e^{-} + p$ serves to highlight this formalism, and the results obtained manifest the entanglement of the three involved processes: the production, propagation, and absorption of neutrinos.