proverb/ˌuna ɡolonˌdɾina ˌno ˌaθe beˈɾano/
one swallow does not a summer make
Literally, “one swallow doesn't make summer”, a calque of Ancient Greek μία χελιδὼν ἔαρ οὐ ποιεῖ (mía khelidṑn éar ou poieî, “one swallow does not a spring make”). The reference to summer instead of spring is shared across European languages; see the descendants at the Ancient Greek entry for more.