Examples

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purely leptonic

$$\mu^{-} \rightarrow e^{-} + \nu_{\mu} +\bar{\nu}_{e}$$

$$\mu^{+} \rightarrow e^{+} + \bar{\nu}_{\mu} + \nu_{e}$$

$$\nu_{\mu} + e \rightarrow \nu_{\mu} + e$$

$$\tau^{-} \rightarrow \mu^{-} + \bar{\nu}_{\mu} + \nu_{\tau}$$

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semi-leptonic

a) without change of strageness ($\Delta S = 0$)

$$n \rightarrow p + e^{-} + \bar{\nu}_{e}$$

$$\mu^{-} + p \rightarrow n + \nu_{\mu}$$

$$\pi^{+} \rightarrow \mu^{+} + \nu_{\mu}$$

b) with change of strangeness ($\Delta S = 1$)

$$\Lambda \rightarrow p + e^{-} + \bar{\nu}_{e}$$

$$K^{+} \rightarrow \mu^{+} + \nu_{\mu}$$

$$\Sigma^{-} \rightarrow n + e^{-} + \bar{\nu}_{e}$$

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semi-hadronic

$$\tau^{-} \rightarrow \pi^{-} + \nu_{\tau}$$

$$\tau^{-} \rightarrow a_{1}(1260) + \nu_{\tau}$$

$$\tau^{-} \rightarrow \rho^{0} + \pi^{0} + \pi^{-} + \nu_{\tau}$$

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purely hadronic (or non-leptonic)

$$\Lambda^{0} \rightarrow \pi^{-} + p$$

$$\Sigma^{+} \rightarrow \pi^{0} + p$$

$$\Omega^{-} \rightarrow \Lambda^{0} + K^{-}$$

Before entering the analysis of the hadronic current, it would be interesting to comment that leptons have quantum numbers $L_{e}$, $L_{\mu}$ and $L_{\tau}$ meaning leptonic number of electron, muon and tau, respectively. They are used to identify those three types of leptons and it is experimentally found that the leptonic quantum number of electron, muon and tau are separately conserved in the weak reactions.