Some verbs rarely appear without se . Learn them as a unit:

In Spanish, standard transitive verbs often imply that the subject is an active, willing agent. However, adding the reflexive pronoun often signals that the event was unintentional or happened to the subject rather than by the subject. This is often called the "Accidental Se."

Most reflexive verbs relate to , personal care, or changes in state. Spanish Reflexive Verbs | Lingvist

| Normal Verb | Meaning | Reflexive Verb | Meaning | |-------------|---------|----------------|---------| | | to wash (something) | Lavarse | to wash oneself | | Duchar | to shower (someone) | Ducharse | to shower (oneself) | | Ir | to go | Irse | to go away / leave | | Llamar | to call | Llamarse | to be called (name) | | Poner | to put | Ponerse | to put on (clothes) / to become | | Acostar | to put to bed | Acostarse | to go to bed (o→ue stem change) | | Despertar | to wake (someone) | Despertarse | to wake up (e→ie) | | Sentir | to feel | Sentirse | to feel (emotion/state) (e→ie) | | Divertir | to amuse | Divertirse | to have fun (e→ie) |

If you just say Yo lavo (I wash), it's incomplete: you wash something else (the car, the dog).