I often notice my students misusing the verbs fermare and smettere, and I understand that the confusion comes from the fact that both verbs are translated into English with to stop.
In Italian fermare and smettere are used differently, depending on the nature of the action they are stopping.
Let’s see how to use them correctly:
Fermare means to stop something or somebody and describe a movement that is physically stopped by an intervention from outside.
Ho fermato la macchina (I stopped the car)
Finalmente ho fermato quella ragazza che piaceva tanto per chiedere il numero (Finally I stopped that girl that I liked so much to ask for her phone number)
As you can see when the action described by the verb is transitive (meaning the verb is followed by a direct or indirect object like ‘la macchina’ or ‘la ragazza’ the verb is normal. However, if the action is intransitive (the verb does not have an object ) the verb take the reflexive form.
L’autobus si è fermato (The bus stopped)
Mi sono fermato al bar perché c’erano i miei amici (I stopped by the bar because some friends of mine were there)
Smettere means to stop doing something and does not involve an idea of movement.
In short, it has the meaning of ceasing and quitting and is always followed by the preposition DI and the infinitive verb. It can never be followed by a noun (
ho smesso di lavoro)
Vorrei smettere di fumare (I’d like to quit smoking)
Ho smesso di lavorare per dedicarmi alla mia famiglia (I stopped working to spend more time with my family)
Attenzione! Smettere has an irregular past tense: ho smesso, hai smesso, etc