When was Venus understood to be not a star but a planet?

[Vivaldi]

When was Venus understood to be not a star but a planet?

[abc3643]

It was always thought of as a planet, but the question is when was the nature of what a planet is understood?

Specifically, Mercury, Venus, Mars, Jupiter, and Saturn are the 5 planets known from antiquity. The etymology for the word "planet" comes from Greek for "wandering stars".
https://www.etymonline.com/word/planet
So, the real question that puzzled the ancient world was why these 5 "wandered the sky" while the other stars were "fixed in the sky" and in the same place year after year.
It wasn't until the invention of the telescope that these questions began to be answered.

Frankly, I don't even think astronomers can adequately agree on what a planet is despite the August 2006 IAU resolutions defining a planet (and which demoted Pluto from planet to dwarf planet), dwarf planet, and other terms. You can read the resolutions here:
www.iau.org/news/pressreleases/detail/iau0603/

[Wise4myage]

I've never heard that before, I think its always considered to be a planet.

[artstatues]

I believe Galileo was the first one, who identified Venus as a planet, however it had been observed by ancient astronomers from different cultures before that