se

A reflexive or reciprocal pronoun: oneself, himself, herself, itself, yourself; themselves; yourselves; each other; one another; A pronoun used with transitive verbs to create the passive voice; A pronoun used with a verb conjugated in the third-person singular to convey an impersonal meaning; Used to third person subjunctive moods to form an impersonal imperative.

“Juan se lava.” — Juan washes himself.

Etymology tree Proto-Indo-European *swé Latin sē Spanish se Inherited from Latin sē.

used instead of indirect object pronouns le and les before the direct object pronouns lo, la, los, or las

“El samaritano se las dio.” — The Samaritan gave them to him.

From Old Spanish ge (from Latin illī, compare Portuguese lhe, Italian gli), whose pronunciation shifted from /ʒe/ to /ʃe/ in Early Modern Spanish, at which point it was reanalyzed as /se/ (rather than shifting to /xe/ as expected).