auxiliary N4 common casual
〜てやる / やる — (casual benefactive) do something for someone (inferior/inti
〜てやる / やる ・ てやる
Meaning
- the casual down-directed benefactive 〜てやる — same construction taught at てやる (te-yaru)
Key sentence
弟に宿題を教えてやった。
I taught my little brother his homework.
Easily confused with
てやる Same benefactive 〜てやる ('do ~ for an inferior/animal', plus the defiant 'I'll do it' sense). The full two-sense teaching layer lives at てやる. For the plain verb やる meaning 'to do', see やる (yaru-3). やる Separate from this auxiliary: bare やる as a main verb means 'to do' (casual する) — taught at やる (yaru-3).
See 〜てやる / やる in real sentences
Jengo shows 〜てやる / やる the way you actually meet it: inside real Japanese sentences, so it sticks instead of staying an abstract rule.
Study it in JengoSources Compiled with reference to A Dictionary of Basic Japanese Grammar. Editorial confidence: medium.