ŝiri

Ŝiri is transitive, permanently, and that is the whole grammar lesson on this page. Something tears something else: ŝi ŝiris la paperon. If the thing comes apart on its own, with no hand on it, you need ŝiriĝi: la papero ŝiriĝis, the paper tore. English happily uses one verb for both jobs, which is exactly why the distinction is worth drilling here rather than discovering later. The general rule and the list of pairs that catch English speakers are in Transitivity.

Against its neighbours it is the violent one. Tranĉi is to cut, and it implies a blade and an intention. Rompi is to break, and it implies a rigid thing giving way. Ŝiri implies fibres pulling apart under force, so paper, cloth, leaves, flesh and the fabric of things generally. It is also the right verb for tearing something away from something else, which is why the wind does it to leaves.

The prefixes multiply it usefully and predictably. Disŝiri is to tear to shreds, elŝiri is to tear out (a page, a weed, a confession), forŝiri is to tear off and away. Figuratively it does what English does: la novaĵo ŝiris lian koron. One matter of spelling, since it bites in this band more than most: the hat is not decoration. Written without it the word is not a word, and if you are typing on a keyboard that will not make ŝ, the x-convention sxiri is the accepted fallback rather than bare siri.